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 $184.77   5.739%   $195.374   $195.37   $195.35   $195.40  
  Purchase #2 $67.25   9.198%   $73.4357   $73.44   $73.45   $73.40  
  Purchase #3 $105.84   11.824%   $118.3545   $118.35   $118.35   $118.40  
  Purchase #4 $152.97   5.349%   $161.1524   $161.15   $161.15   $161.20  
  Purchase #5 $21.94   12.249%   $24.6274   $24.63   $24.65   $24.60  
  Purchase #6 $66.91   9.448%   $73.2317   $73.23   $73.25   $73.20  
  Purchase #7 $100.48   11.563%   $112.0985   $112.10   $112.10   $112.10  
  7 purchase totals = $700.16       $758.2742   $758.27   $758.30   $758.30