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 $44.95   8.145%   $48.6112   $48.61   $48.60   $48.60  
  Purchase #2 $121.74   7.673%   $131.0811   $131.08   $131.10   $131.10  
  Purchase #3 $85.99   8.394%   $93.208   $93.21   $93.20   $93.20  
  Purchase #4 $54.77   11.213%   $60.9114   $60.91   $60.90   $60.90  
  Purchase #5 $146.35   6.161%   $155.3666   $155.37   $155.35   $155.40  
  Purchase #6 $159.48   10.231%   $175.7964   $175.80   $175.80   $175.80  
  Purchase #7 $50.68   5.678%   $53.5576   $53.56   $53.55   $53.60  
  7 purchase totals = $663.96       $718.5323   $718.54   $718.50   $718.60