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 $57.26   6.439%   $60.947   $60.95   $60.95   $60.90  
  Purchase #2 $100.50   12.813%   $113.3771   $113.38   $113.40   $113.40  
  Purchase #3 $153.62   12.567%   $172.9254   $172.93   $172.95   $172.90  
  Purchase #4 $44.51   8.534%   $48.3085   $48.31   $48.30   $48.30  
  Purchase #5 $181.30   6.685%   $193.4199   $193.42   $193.40   $193.40  
  Purchase #6 $96.46   6.167%   $102.4087   $102.41   $102.40   $102.40  
  Purchase #7 $139.54   11.340%   $155.3638   $155.36   $155.35   $155.40  
  7 purchase totals = $773.19       $846.7504   $846.76   $846.75   $846.70