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 $68.55   3.204%   $70.7463   $70.75   $70.75   $70.70  
  Purchase #2 $214.41   9.414%   $234.5946   $234.59   $234.60   $234.60  
  Purchase #3 $75.57   4.427%   $78.9155   $78.92   $78.90   $78.90  
  Purchase #4 $60.77   13.380%   $68.901   $68.90   $68.90   $68.90  
  Purchase #5 $213.32   12.385%   $239.7397   $239.74   $239.75   $239.70  
  Purchase #6 $112.35   5.806%   $118.873   $118.87   $118.85   $118.90  
  Purchase #7 $12.78   10.620%   $14.1372   $14.14   $14.15   $14.10  
  7 purchase totals = $757.75       $825.9073   $825.91   $825.90   $825.80