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 $67.47   8.388%   $73.1294   $73.13   $73.15   $73.10  
  Purchase #2 $246.62   9.863%   $270.9441   $270.94   $270.95   $270.90  
  Purchase #3 $87.51   9.762%   $96.0527   $96.05   $96.05   $96.10  
  Purchase #4 $164.54   10.859%   $182.4074   $182.41   $182.40   $182.40  
  Purchase #5 $206.96   6.172%   $219.7336   $219.73   $219.75   $219.70  
  Purchase #6 $114.76   11.713%   $128.2018   $128.20   $128.20   $128.20  
  Purchase #7 $93.68   8.207%   $101.3683   $101.37   $101.35   $101.40  
  7 purchase totals = $981.54       $1,071.8373   $1,071.83   $1,071.85   $1,071.80