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 $65.49   10.193%   $72.1654   $72.17   $72.15   $72.20  
  Purchase #2 $6.76   12.525%   $7.6067   $7.61   $7.60   $7.60  
  Purchase #3 $40.58   13.706%   $46.1419   $46.14   $46.15   $46.10  
  Purchase #4 $240.95   5.766%   $254.8432   $254.84   $254.85   $254.80  
  Purchase #5 $194.75   11.826%   $217.7811   $217.78   $217.80   $217.80  
  Purchase #6 $182.86   11.220%   $203.3769   $203.38   $203.40   $203.40  
  Purchase #7 $88.49   5.853%   $93.6693   $93.67   $93.65   $93.70  
  7 purchase totals = $819.88       $895.5845   $895.59   $895.60   $895.60