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 $67.41   11.104%   $74.8952   $74.90   $74.90   $74.90  
  Purchase #2 $244.94   6.176%   $260.0675   $260.07   $260.05   $260.10  
  Purchase #3 $69.65   11.568%   $77.7071   $77.71   $77.70   $77.70  
  Purchase #4 $183.77   6.397%   $195.5258   $195.53   $195.55   $195.50  
  Purchase #5 $156.87   3.528%   $162.4044   $162.40   $162.40   $162.40  
  Purchase #6 $132.61   7.171%   $142.1195   $142.12   $142.10   $142.10  
  Purchase #7 $228.92   7.434%   $245.9379   $245.94   $245.95   $245.90  
  7 purchase totals = $1,084.17       $1,158.6574   $1,158.67   $1,158.65   $1,158.60