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 $24.40   7.389%   $26.2029   $26.20   $26.20   $26.20  
  Purchase #2 $180.30   6.314%   $191.6841   $191.68   $191.70   $191.70  
  Purchase #3 $98.71   4.672%   $103.3217   $103.32   $103.30   $103.30  
  Purchase #4 $53.92   5.416%   $56.8403   $56.84   $56.85   $56.80  
  Purchase #5 $138.92   7.467%   $149.2932   $149.29   $149.30   $149.30  
  Purchase #6 $89.48   10.311%   $98.7063   $98.71   $98.70   $98.70  
  Purchase #7 $118.27   6.575%   $126.0463   $126.05   $126.05   $126.00  
  7 purchase totals = $704.00       $752.0948   $752.09   $752.10   $752.00