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 $87.54   12.590%   $98.5613   $98.56   $98.55   $98.60  
  Purchase #2 $223.41   11.568%   $249.2541   $249.25   $249.25   $249.30  
  Purchase #3 $232.90   8.689%   $253.1367   $253.14   $253.15   $253.10  
  Purchase #4 $168.77   4.237%   $175.9208   $175.92   $175.90   $175.90  
  Purchase #5 $218.85   5.341%   $230.5388   $230.54   $230.55   $230.50  
  Purchase #6 $42.86   4.388%   $44.7407   $44.74   $44.75   $44.70  
  Purchase #7 $195.60   9.184%   $213.5639   $213.56   $213.55   $213.60  
  7 purchase totals = $1,169.93       $1,265.7163   $1,265.71   $1,265.70   $1,265.70