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 $64.38   7.792%   $69.3965   $69.40   $69.40   $69.40  
  Purchase #2 $210.73   10.208%   $232.2413   $232.24   $232.25   $232.20  
  Purchase #3 $153.76   11.361%   $171.2287   $171.23   $171.25   $171.20  
  Purchase #4 $170.60   3.117%   $175.9176   $175.92   $175.90   $175.90  
  Purchase #5 $152.56   5.272%   $160.603   $160.60   $160.60   $160.60  
  Purchase #6 $125.88   10.813%   $139.4914   $139.49   $139.50   $139.50  
  Purchase #7 $241.61   4.137%   $251.6054   $251.61   $251.60   $251.60  
  7 purchase totals = $1,119.52       $1,200.4839   $1,200.49   $1,200.50   $1,200.40