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 $62.27   7.514%   $66.949   $66.95   $66.95   $66.90  
  Purchase #2 $15.61   10.583%   $17.262   $17.26   $17.25   $17.30  
  Purchase #3 $23.72   3.755%   $24.6107   $24.61   $24.60   $24.60  
  Purchase #4 $195.77   4.579%   $204.7343   $204.73   $204.75   $204.70  
  Purchase #5 $82.76   3.585%   $85.7269   $85.73   $85.75   $85.70  
  Purchase #6 $116.62   12.466%   $131.1578   $131.16   $131.15   $131.20  
  Purchase #7 $219.34   7.654%   $236.1283   $236.13   $236.15   $236.10  
  7 purchase totals = $716.09       $766.5690   $766.57   $766.60   $766.50