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 $117.85   6.771%   $125.8296   $125.83   $125.85   $125.80  
  Purchase #2 $131.67   11.284%   $146.5276   $146.53   $146.55   $146.50  
  Purchase #3 $204.30   10.576%   $225.9068   $225.91   $225.90   $225.90  
  Purchase #4 $140.83   5.444%   $148.4968   $148.50   $148.50   $148.50  
  Purchase #5 $95.76   6.207%   $101.7038   $101.70   $101.70   $101.70  
  Purchase #6 $191.62   3.411%   $198.1562   $198.16   $198.15   $198.20  
  Purchase #7 $246.84   9.134%   $269.3864   $269.39   $269.40   $269.40  
  7 purchase totals = $1,128.87       $1,216.0072   $1,216.02   $1,216.05   $1,216.00