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 $222.42   5.803%   $235.327   $235.33   $235.35   $235.30  
  Purchase #2 $187.45   11.262%   $208.5606   $208.56   $208.55   $208.60  
  Purchase #3 $150.73   7.796%   $162.4809   $162.48   $162.50   $162.50  
  Purchase #4 $248.49   9.162%   $271.2567   $271.26   $271.25   $271.30  
  Purchase #5 $187.76   6.781%   $200.492   $200.49   $200.50   $200.50  
  Purchase #6 $137.45   6.160%   $145.9169   $145.92   $145.90   $145.90  
  Purchase #7 $216.74   8.335%   $234.8053   $234.81   $234.80   $234.80  
  7 purchase totals = $1,351.04       $1,458.8394   $1,458.85   $1,458.85   $1,458.90