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 $160.53   13.388%   $182.0218   $182.02   $182.00   $182.00  
  Purchase #2 $85.60   8.327%   $92.7279   $92.73   $92.75   $92.70  
  Purchase #3 $201.38   6.120%   $213.7045   $213.70   $213.70   $213.70  
  Purchase #4 $151.89   6.226%   $161.3467   $161.35   $161.35   $161.30  
  Purchase #5 $87.49   11.555%   $97.5995   $97.60   $97.60   $97.60  
  Purchase #6 $14.86   8.601%   $16.1381   $16.14   $16.15   $16.10  
  Purchase #7 $107.52   5.581%   $113.5207   $113.52   $113.50   $113.50  
  7 purchase totals = $809.27       $877.0592   $877.06   $877.05   $876.90