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 $60.94   8.207%   $65.9413   $65.94   $65.95   $65.90  
  Purchase #2 $205.76   6.803%   $219.7579   $219.76   $219.75   $219.80  
  Purchase #3 $46.33   12.814%   $52.2667   $52.27   $52.25   $52.30  
  Purchase #4 $161.86   7.839%   $174.5482   $174.55   $174.55   $174.50  
  Purchase #5 $130.26   3.748%   $135.1421   $135.14   $135.15   $135.10  
  Purchase #6 $68.28   6.584%   $72.7756   $72.78   $72.80   $72.80  
  Purchase #7 $225.35   5.741%   $238.2873   $238.29   $238.30   $238.30  
  7 purchase totals = $898.78       $958.7191   $958.73   $958.75   $958.70