Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $177.81   10.570%   $196.6045   $196.60   $196.60   $196.60  
  Purchase #2 $153.80   13.761%   $174.9644   $174.96   $174.95   $175.00  
  Purchase #3 $240.56   3.454%   $248.8689   $248.87   $248.85   $248.90  
  Purchase #4 $238.93   5.209%   $251.3759   $251.38   $251.40   $251.40  
  Purchase #5 $173.50   3.322%   $179.2637   $179.26   $179.25   $179.30  
  Purchase #6 $129.28   10.703%   $143.1168   $143.12   $143.10   $143.10  
  Purchase #7 $160.25   8.352%   $173.6341   $173.63   $173.65   $173.60  
  7 purchase totals = $1,274.13       $1,367.8283   $1,367.82   $1,367.80   $1,367.90