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 $68.28   3.613%   $70.747   $70.75   $70.75   $70.70  
  Purchase #2 $235.80   13.528%   $267.699   $267.70   $267.70   $267.70  
  Purchase #3 $54.39   8.288%   $58.8978   $58.90   $58.90   $58.90  
  Purchase #4 $20.34   4.461%   $21.2474   $21.25   $21.25   $21.20  
  Purchase #5 $205.50   5.754%   $217.3245   $217.32   $217.30   $217.30  
  Purchase #6 $139.26   9.530%   $152.5315   $152.53   $152.55   $152.50  
  Purchase #7 $137.58   8.238%   $148.9138   $148.91   $148.90   $148.90  
  7 purchase totals = $861.15       $937.3610   $937.36   $937.35   $937.20