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 $59.85   3.402%   $61.8861   $61.89   $61.90   $61.90  
  Purchase #2 $215.72   13.736%   $245.3513   $245.35   $245.35   $245.40  
  Purchase #3 $244.36   6.539%   $260.3387   $260.34   $260.35   $260.30  
  Purchase #4 $228.95   5.333%   $241.1599   $241.16   $241.15   $241.20  
  Purchase #5 $207.35   6.730%   $221.3047   $221.30   $221.30   $221.30  
  Purchase #6 $87.91   4.138%   $91.5477   $91.55   $91.55   $91.50  
  Purchase #7 $242.55   7.326%   $260.3192   $260.32   $260.30   $260.30  
  7 purchase totals = $1,286.69       $1,381.9076   $1,381.91   $1,381.90   $1,381.90