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 $85.38   11.515%   $95.2115   $95.21   $95.20   $95.20  
  Purchase #2 $227.60   10.303%   $251.0496   $251.05   $251.05   $251.00  
  Purchase #3 $132.82   3.634%   $137.6467   $137.65   $137.65   $137.60  
  Purchase #4 $159.74   5.798%   $169.0017   $169.00   $169.00   $169.00  
  Purchase #5 $244.96   12.668%   $275.9915   $275.99   $276.00   $276.00  
  Purchase #6 $72.89   5.677%   $77.028   $77.03   $77.05   $77.00  
  Purchase #7 $211.71   5.724%   $223.8283   $223.83   $223.85   $223.80  
  7 purchase totals = $1,135.10       $1,229.7573   $1,229.76   $1,229.80   $1,229.60