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 $193.58   5.823%   $204.8522   $204.85   $204.85   $204.90  
  Purchase #2 $53.30   6.376%   $56.6984   $56.70   $56.70   $56.70  
  Purchase #3 $235.61   3.775%   $244.5043   $244.50   $244.50   $244.50  
  Purchase #4 $178.70   3.718%   $185.3441   $185.34   $185.35   $185.30  
  Purchase #5 $125.33   5.507%   $132.2319   $132.23   $132.25   $132.20  
  Purchase #6 $139.93   3.697%   $145.1032   $145.10   $145.10   $145.10  
  Purchase #7 $139.92   10.228%   $154.231   $154.23   $154.25   $154.20  
  7 purchase totals = $1,066.37       $1,122.9651   $1,122.95   $1,123.00   $1,122.90