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 $176.65   9.633%   $193.6667   $193.67   $193.65   $193.70  
  Purchase #2 $244.42   6.833%   $261.1212   $261.12   $261.10   $261.10  
  Purchase #3 $107.46   10.721%   $118.9808   $118.98   $119.00   $119.00  
  Purchase #4 $237.77   3.232%   $245.4547   $245.45   $245.45   $245.50  
  Purchase #5 $217.71   7.375%   $233.7661   $233.77   $233.75   $233.80  
  Purchase #6 $202.33   7.118%   $216.7318   $216.73   $216.75   $216.70  
  Purchase #7 $204.63   13.110%   $231.457   $231.46   $231.45   $231.50  
  7 purchase totals = $1,390.97       $1,501.1783   $1,501.18   $1,501.15   $1,501.30