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 $7.54   5.210%   $7.9328   $7.93   $7.95   $7.90  
  Purchase #2 $59.51   4.143%   $61.9755   $61.98   $62.00   $62.00  
  Purchase #3 $103.85   3.582%   $107.5699   $107.57   $107.55   $107.60  
  Purchase #4 $169.88   7.461%   $182.5547   $182.55   $182.55   $182.60  
  Purchase #5 $91.38   11.829%   $102.1893   $102.19   $102.20   $102.20  
  Purchase #6 $136.87   9.509%   $149.885   $149.89   $149.90   $149.90  
  Purchase #7 $228.39   12.131%   $256.096   $256.10   $256.10   $256.10  
  7 purchase totals = $797.42       $868.2032   $868.21   $868.25   $868.30