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 $205.25   4.679%   $214.8536   $214.85   $214.85   $214.90  
  Purchase #2 $6.87   11.622%   $7.6684   $7.67   $7.65   $7.70  
  Purchase #3 $70.64   3.488%   $73.1039   $73.10   $73.10   $73.10  
  Purchase #4 $15.98   12.659%   $18.0029   $18.00   $18.00   $18.00  
  Purchase #5 $163.84   13.542%   $186.0272   $186.03   $186.05   $186.00  
  Purchase #6 $15.28   11.404%   $17.0225   $17.02   $17.00   $17.00  
  Purchase #7 $236.31   3.394%   $244.3304   $244.33   $244.35   $244.30  
  7 purchase totals = $714.17       $761.0089   $761.00   $761.00   $761.00