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 $194.41   5.736%   $205.5614   $205.56   $205.55   $205.60  
  Purchase #2 $44.64   4.160%   $46.497   $46.50   $46.50   $46.50  
  Purchase #3 $107.38   3.164%   $110.7775   $110.78   $110.80   $110.80  
  Purchase #4 $27.83   5.180%   $29.2716   $29.27   $29.25   $29.30  
  Purchase #5 $177.37   13.399%   $201.1358   $201.14   $201.15   $201.10  
  Purchase #6 $12.64   4.460%   $13.2037   $13.20   $13.20   $13.20  
  Purchase #7 $117.37   11.539%   $130.9133   $130.91   $130.90   $130.90  
  7 purchase totals = $681.64       $737.3603   $737.36   $737.35   $737.40