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 $119.77   5.327%   $126.1501   $126.15   $126.15   $126.20  
  Purchase #2 $245.99   8.742%   $267.4944   $267.49   $267.50   $267.50  
  Purchase #3 $160.53   5.705%   $169.6882   $169.69   $169.70   $169.70  
  Purchase #4 $29.65   8.675%   $32.2221   $32.22   $32.20   $32.20  
  Purchase #5 $20.67   3.642%   $21.4228   $21.42   $21.40   $21.40  
  Purchase #6 $29.93   9.176%   $32.6764   $32.68   $32.70   $32.70  
  Purchase #7 $121.48   8.380%   $131.66   $131.66   $131.65   $131.70  
  7 purchase totals = $728.02       $781.3140   $781.31   $781.30   $781.40