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 $53.25   10.550%   $58.8679   $58.87   $58.85   $58.90  
  Purchase #2 $136.35   9.161%   $148.841   $148.84   $148.85   $148.80  
  Purchase #3 $53.35   10.686%   $59.051   $59.05   $59.05   $59.10  
  Purchase #4 $10.92   11.626%   $12.1896   $12.19   $12.20   $12.20  
  Purchase #5 $35.85   7.523%   $38.547   $38.55   $38.55   $38.50  
  Purchase #6 $195.81   4.572%   $204.7624   $204.76   $204.75   $204.80  
  Purchase #7 $246.69   5.543%   $260.364   $260.36   $260.35   $260.40  
  7 purchase totals = $732.22       $782.6229   $782.62   $782.60   $782.70