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 $88.69   8.138%   $95.9076   $95.91   $95.90   $95.90  
  Purchase #2 $143.80   10.321%   $158.6416   $158.64   $158.65   $158.60  
  Purchase #3 $152.47   5.730%   $161.2065   $161.21   $161.20   $161.20  
  Purchase #4 $165.35   10.607%   $182.8887   $182.89   $182.90   $182.90  
  Purchase #5 $179.84   12.195%   $201.7715   $201.77   $201.75   $201.80  
  Purchase #6 $144.48   9.104%   $157.6335   $157.63   $157.65   $157.60  
  Purchase #7 $94.39   10.536%   $104.3349   $104.33   $104.35   $104.30  
  7 purchase totals = $969.02       $1,062.3843   $1,062.38   $1,062.40   $1,062.30