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 $84.71   12.533%   $95.3267   $95.33   $95.35   $95.30  
  Purchase #2 $214.51   4.346%   $223.8326   $223.83   $223.85   $223.80  
  Purchase #3 $56.56   3.670%   $58.6358   $58.64   $58.65   $58.60  
  Purchase #4 $185.49   4.131%   $193.1526   $193.15   $193.15   $193.20  
  Purchase #5 $249.28   8.851%   $271.3438   $271.34   $271.35   $271.30  
  Purchase #6 $245.85   11.205%   $273.3975   $273.40   $273.40   $273.40  
  Purchase #7 $61.73   12.827%   $69.6481   $69.65   $69.65   $69.60  
  7 purchase totals = $1,098.13       $1,185.3371   $1,185.34   $1,185.40   $1,185.20