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 $86.65   9.559%   $94.9329   $94.93   $94.95   $94.90  
  Purchase #2 $130.29   5.733%   $137.7595   $137.76   $137.75   $137.80  
  Purchase #3 $173.86   5.226%   $182.9459   $182.95   $182.95   $182.90  
  Purchase #4 $121.27   11.428%   $135.1287   $135.13   $135.15   $135.10  
  Purchase #5 $145.85   10.660%   $161.3976   $161.40   $161.40   $161.40  
  Purchase #6 $158.64   7.220%   $170.0938   $170.09   $170.10   $170.10  
  Purchase #7 $153.80   5.315%   $161.9745   $161.97   $161.95   $162.00  
  7 purchase totals = $970.36       $1,044.2329   $1,044.23   $1,044.25   $1,044.20