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 $62.99   10.694%   $69.7262   $69.73   $69.75   $69.70  
  Purchase #2 $30.61   6.532%   $32.6094   $32.61   $32.60   $32.60  
  Purchase #3 $112.73   3.212%   $116.3509   $116.35   $116.35   $116.40  
  Purchase #4 $189.55   5.590%   $200.1458   $200.15   $200.15   $200.10  
  Purchase #5 $205.38   6.279%   $218.2758   $218.28   $218.30   $218.30  
  Purchase #6 $139.78   8.866%   $152.1729   $152.17   $152.15   $152.20  
  Purchase #7 $152.29   6.407%   $162.0472   $162.05   $162.05   $162.00  
  7 purchase totals = $893.33       $951.3282   $951.34   $951.35   $951.30