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 $62.86   6.748%   $67.1018   $67.10   $67.10   $67.10  
  Purchase #2 $175.79   6.743%   $187.6435   $187.64   $187.65   $187.60  
  Purchase #3 $105.37   10.425%   $116.3548   $116.35   $116.35   $116.40  
  Purchase #4 $94.53   5.543%   $99.7698   $99.77   $99.75   $99.80  
  Purchase #5 $212.83   12.852%   $240.1829   $240.18   $240.20   $240.20  
  Purchase #6 $120.82   3.502%   $125.0511   $125.05   $125.05   $125.10  
  Purchase #7 $111.34   4.782%   $116.6643   $116.66   $116.65   $116.70  
  7 purchase totals = $883.54       $952.7682   $952.75   $952.75   $952.90