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 $32.41   3.866%   $33.663   $33.66   $33.65   $33.70  
  Purchase #2 $111.39   12.415%   $125.2191   $125.22   $125.20   $125.20  
  Purchase #3 $231.74   9.773%   $254.388   $254.39   $254.40   $254.40  
  Purchase #4 $127.61   4.150%   $132.9058   $132.91   $132.90   $132.90  
  Purchase #5 $195.46   4.251%   $203.769   $203.77   $203.75   $203.80  
  Purchase #6 $154.26   5.282%   $162.408   $162.41   $162.40   $162.40  
  Purchase #7 $215.93   13.801%   $245.7305   $245.73   $245.75   $245.70  
  7 purchase totals = $1,068.80       $1,158.0834   $1,158.09   $1,158.05   $1,158.10