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 $58.75   5.620%   $62.0518   $62.05   $62.05   $62.10  
  Purchase #2 $146.96   12.265%   $164.9846   $164.98   $165.00   $165.00  
  Purchase #3 $208.32   13.642%   $236.739   $236.74   $236.75   $236.70  
  Purchase #4 $244.29   10.217%   $269.2491   $269.25   $269.25   $269.20  
  Purchase #5 $226.73   13.538%   $257.4247   $257.42   $257.40   $257.40  
  Purchase #6 $102.92   12.734%   $116.0258   $116.03   $116.05   $116.00  
  Purchase #7 $14.82   3.786%   $15.3811   $15.38   $15.40   $15.40  
  7 purchase totals = $1,002.79       $1,121.8561   $1,121.85   $1,121.90   $1,121.80