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 $105.93   7.610%   $113.9913   $113.99   $114.00   $114.00  
  Purchase #2 $237.58   12.554%   $267.4058   $267.41   $267.40   $267.40  
  Purchase #3 $64.37   6.511%   $68.5611   $68.56   $68.55   $68.60  
  Purchase #4 $99.29   3.786%   $103.0491   $103.05   $103.05   $103.00  
  Purchase #5 $39.38   6.227%   $41.8322   $41.83   $41.85   $41.80  
  Purchase #6 $60.57   6.162%   $64.3023   $64.30   $64.30   $64.30  
  Purchase #7 $152.92   13.173%   $173.0642   $173.06   $173.05   $173.10  
  7 purchase totals = $760.04       $832.2060   $832.20   $832.20   $832.20