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 $246.60   6.519%   $262.6759   $262.68   $262.70   $262.70  
  Purchase #2 $19.75   10.863%   $21.8954   $21.90   $21.90   $21.90  
  Purchase #3 $79.80   5.155%   $83.9137   $83.91   $83.90   $83.90  
  Purchase #4 $46.37   11.332%   $51.6246   $51.62   $51.60   $51.60  
  Purchase #5 $228.54   6.154%   $242.6044   $242.60   $242.60   $242.60  
  Purchase #6 $196.66   4.849%   $206.196   $206.20   $206.20   $206.20  
  Purchase #7 $165.61   5.733%   $175.1044   $175.10   $175.10   $175.10  
  7 purchase totals = $983.33       $1,044.0144   $1,044.01   $1,044.00   $1,044.00