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 $244.78   7.131%   $262.2353   $262.24   $262.25   $262.20  
  Purchase #2 $104.93   4.535%   $109.6886   $109.69   $109.70   $109.70  
  Purchase #3 $239.44   5.846%   $253.4377   $253.44   $253.45   $253.40  
  Purchase #4 $104.31   11.848%   $116.6686   $116.67   $116.65   $116.70  
  Purchase #5 $62.30   4.265%   $64.9571   $64.96   $64.95   $65.00  
  Purchase #6 $27.26   5.464%   $28.7495   $28.75   $28.75   $28.70  
  Purchase #7 $203.63   10.569%   $225.1517   $225.15   $225.15   $225.20  
  7 purchase totals = $986.65       $1,060.8885   $1,060.90   $1,060.90   $1,060.90