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 $84.52   13.508%   $95.937   $95.94   $95.95   $95.90  
  Purchase #2 $211.59   11.660%   $236.2614   $236.26   $236.25   $236.30  
  Purchase #3 $12.86   12.857%   $14.5134   $14.51   $14.50   $14.50  
  Purchase #4 $165.28   5.826%   $174.9092   $174.91   $174.90   $174.90  
  Purchase #5 $17.27   6.225%   $18.3451   $18.35   $18.35   $18.30  
  Purchase #6 $185.73   5.288%   $195.5514   $195.55   $195.55   $195.60  
  Purchase #7 $109.33   12.343%   $122.8246   $122.82   $122.80   $122.80  
  7 purchase totals = $786.58       $858.3421   $858.34   $858.30   $858.30