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 $224.77   7.280%   $241.1333   $241.13   $241.15   $241.10  
  Purchase #2 $193.43   9.326%   $211.4693   $211.47   $211.45   $211.50  
  Purchase #3 $225.37   3.213%   $232.6111   $232.61   $232.60   $232.60  
  Purchase #4 $238.88   5.212%   $251.3304   $251.33   $251.35   $251.30  
  Purchase #5 $82.40   8.598%   $89.4848   $89.48   $89.50   $89.50  
  Purchase #6 $72.38   3.760%   $75.1015   $75.10   $75.10   $75.10  
  Purchase #7 $152.95   5.221%   $160.9355   $160.94   $160.95   $160.90  
  7 purchase totals = $1,190.18       $1,262.0659   $1,262.06   $1,262.10   $1,262.00