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 $93.29   4.402%   $97.3966   $97.40   $97.40   $97.40  
  Purchase #2 $231.45   9.461%   $253.3475   $253.35   $253.35   $253.30  
  Purchase #3 $30.52   10.641%   $33.7676   $33.77   $33.75   $33.80  
  Purchase #4 $69.56   6.486%   $74.0717   $74.07   $74.05   $74.10  
  Purchase #5 $142.31   13.786%   $161.9289   $161.93   $161.95   $161.90  
  Purchase #6 $243.86   9.725%   $267.5754   $267.58   $267.60   $267.60  
  Purchase #7 $60.50   11.378%   $67.3837   $67.38   $67.40   $67.40  
  7 purchase totals = $871.49       $955.4714   $955.48   $955.50   $955.50