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 $242.98   10.189%   $267.7372   $267.74   $267.75   $267.70  
  Purchase #2 $227.98   9.639%   $249.955   $249.96   $249.95   $250.00  
  Purchase #3 $88.71   3.673%   $91.9683   $91.97   $91.95   $92.00  
  Purchase #4 $8.30   4.295%   $8.6565   $8.66   $8.65   $8.70  
  Purchase #5 $64.45   13.148%   $72.9239   $72.92   $72.90   $72.90  
  Purchase #6 $34.26   7.813%   $36.9367   $36.94   $36.95   $36.90  
  Purchase #7 $32.58   5.570%   $34.3947   $34.39   $34.40   $34.40  
  7 purchase totals = $699.26       $762.5723   $762.58   $762.55   $762.60