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 $61.37   4.243%   $63.9739   $63.97   $63.95   $64.00  
  Purchase #2 $245.87   3.847%   $255.3286   $255.33   $255.35   $255.30  
  Purchase #3 $248.37   7.142%   $266.1086   $266.11   $266.10   $266.10  
  Purchase #4 $92.56   9.624%   $101.468   $101.47   $101.45   $101.50  
  Purchase #5 $43.95   8.390%   $47.6374   $47.64   $47.65   $47.60  
  Purchase #6 $59.96   4.203%   $62.4801   $62.48   $62.50   $62.50  
  Purchase #7 $136.36   10.710%   $150.9642   $150.96   $150.95   $151.00  
  7 purchase totals = $888.44       $947.9608   $947.96   $947.95   $948.00