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 $93.72   3.549%   $97.0461   $97.05   $97.05   $97.00  
  Purchase #2 $159.99   8.864%   $174.1715   $174.17   $174.15   $174.20  
  Purchase #3 $233.82   11.620%   $260.9899   $260.99   $261.00   $261.00  
  Purchase #4 $208.38   6.669%   $222.2769   $222.28   $222.30   $222.30  
  Purchase #5 $194.54   13.652%   $221.0986   $221.10   $221.10   $221.10  
  Purchase #6 $243.51   4.837%   $255.2886   $255.29   $255.30   $255.30  
  Purchase #7 $71.80   4.122%   $74.7596   $74.76   $74.75   $74.80  
  7 purchase totals = $1,205.76       $1,305.6312   $1,305.64   $1,305.65   $1,305.70