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 $56.63   11.281%   $63.0184   $63.02   $63.00   $63.00  
  Purchase #2 $228.26   10.395%   $251.9876   $251.99   $252.00   $252.00  
  Purchase #3 $242.41   11.274%   $269.7393   $269.74   $269.75   $269.70  
  Purchase #4 $95.97   6.354%   $102.0679   $102.07   $102.05   $102.10  
  Purchase #5 $186.71   4.628%   $195.3509   $195.35   $195.35   $195.40  
  Purchase #6 $170.45   7.434%   $183.1213   $183.12   $183.10   $183.10  
  Purchase #7 $148.30   9.728%   $162.7266   $162.73   $162.75   $162.70  
  7 purchase totals = $1,128.73       $1,228.0120   $1,228.02   $1,228.00   $1,228.00