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 $185.77   11.212%   $206.5985   $206.60   $206.60   $206.60  
  Purchase #2 $165.57   9.464%   $181.2395   $181.24   $181.25   $181.20  
  Purchase #3 $224.25   13.241%   $253.9429   $253.94   $253.95   $253.90  
  Purchase #4 $229.64   13.540%   $260.7333   $260.73   $260.75   $260.70  
  Purchase #5 $56.63   10.349%   $62.4906   $62.49   $62.50   $62.50  
  Purchase #6 $48.64   5.318%   $51.2267   $51.23   $51.25   $51.20  
  Purchase #7 $160.73   12.175%   $180.2989   $180.30   $180.30   $180.30  
  7 purchase totals = $1,071.23       $1,196.5304   $1,196.53   $1,196.60   $1,196.40