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 $68.60   9.707%   $75.259   $75.26   $75.25   $75.30  
  Purchase #2 $98.96   6.156%   $105.052   $105.05   $105.05   $105.10  
  Purchase #3 $107.77   9.242%   $117.7301   $117.73   $117.75   $117.70  
  Purchase #4 $242.87   3.190%   $250.6176   $250.62   $250.60   $250.60  
  Purchase #5 $6.85   13.468%   $7.7726   $7.77   $7.75   $7.80  
  Purchase #6 $217.37   11.139%   $241.5828   $241.58   $241.60   $241.60  
  Purchase #7 $76.48   13.708%   $86.9639   $86.96   $86.95   $87.00  
  7 purchase totals = $818.90       $884.9780   $884.97   $884.95   $885.10