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 $68.50   11.117%   $76.1151   $76.12   $76.10   $76.10  
  Purchase #2 $244.51   7.804%   $263.5916   $263.59   $263.60   $263.60  
  Purchase #3 $21.85   7.167%   $23.416   $23.42   $23.40   $23.40  
  Purchase #4 $158.26   10.324%   $174.5988   $174.60   $174.60   $174.60  
  Purchase #5 $95.74   3.142%   $98.7482   $98.75   $98.75   $98.70  
  Purchase #6 $187.31   3.707%   $194.2536   $194.25   $194.25   $194.30  
  Purchase #7 $191.99   12.685%   $216.3439   $216.34   $216.35   $216.30  
  7 purchase totals = $968.16       $1,047.0672   $1,047.07   $1,047.05   $1,047.00