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 $92.58   9.376%   $101.2603   $101.26   $101.25   $101.30  
  Purchase #2 $57.30   10.200%   $63.1446   $63.14   $63.15   $63.10  
  Purchase #3 $190.71   5.549%   $201.2925   $201.29   $201.30   $201.30  
  Purchase #4 $169.59   8.507%   $184.017   $184.02   $184.00   $184.00  
  Purchase #5 $243.54   9.672%   $267.0952   $267.10   $267.10   $267.10  
  Purchase #6 $43.87   4.857%   $46.0008   $46.00   $46.00   $46.00  
  Purchase #7 $144.48   13.327%   $163.7348   $163.73   $163.75   $163.70  
  7 purchase totals = $942.07       $1,026.5452   $1,026.54   $1,026.55   $1,026.50