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 $208.51   10.428%   $230.2534   $230.25   $230.25   $230.30  
  Purchase #2 $63.38   7.702%   $68.2615   $68.26   $68.25   $68.30  
  Purchase #3 $42.91   13.260%   $48.5999   $48.60   $48.60   $48.60  
  Purchase #4 $97.86   4.863%   $102.6189   $102.62   $102.60   $102.60  
  Purchase #5 $208.93   13.369%   $236.8619   $236.86   $236.85   $236.90  
  Purchase #6 $172.87   9.263%   $188.8829   $188.88   $188.90   $188.90  
  Purchase #7 $132.62   12.509%   $149.2094   $149.21   $149.20   $149.20  
  7 purchase totals = $927.08       $1,024.6879   $1,024.68   $1,024.65   $1,024.80