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 $92.66   3.240%   $95.6622   $95.66   $95.65   $95.70  
  Purchase #2 $25.40   9.309%   $27.7645   $27.76   $27.75   $27.80  
  Purchase #3 $185.33   5.812%   $196.1014   $196.10   $196.10   $196.10  
  Purchase #4 $111.44   8.647%   $121.0762   $121.08   $121.10   $121.10  
  Purchase #5 $225.29   5.845%   $238.4582   $238.46   $238.45   $238.50  
  Purchase #6 $231.38   12.402%   $260.0757   $260.08   $260.10   $260.10  
  Purchase #7 $11.63   6.723%   $12.4119   $12.41   $12.40   $12.40  
  7 purchase totals = $883.13       $951.5501   $951.55   $951.55   $951.70