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 $209.33   7.118%   $224.2301   $224.23   $224.25   $224.20  
  Purchase #2 $215.82   6.794%   $230.4828   $230.48   $230.50   $230.50  
  Purchase #3 $164.61   3.847%   $170.9425   $170.94   $170.95   $170.90  
  Purchase #4 $60.58   6.430%   $64.4753   $64.48   $64.50   $64.50  
  Purchase #5 $11.31   3.310%   $11.6844   $11.68   $11.70   $11.70  
  Purchase #6 $208.64   10.445%   $230.4324   $230.43   $230.45   $230.40  
  Purchase #7 $125.59   9.223%   $137.1732   $137.17   $137.15   $137.20  
  7 purchase totals = $995.88       $1,069.4207   $1,069.41   $1,069.50   $1,069.40