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 $73.54   11.568%   $82.0471   $82.05   $82.05   $82.00  
  Purchase #2 $127.50   4.836%   $133.6659   $133.67   $133.65   $133.70  
  Purchase #3 $74.27   3.379%   $76.7796   $76.78   $76.80   $76.80  
  Purchase #4 $187.45   13.783%   $213.2862   $213.29   $213.30   $213.30  
  Purchase #5 $214.92   8.606%   $233.416   $233.42   $233.40   $233.40  
  Purchase #6 $85.94   11.340%   $95.6856   $95.69   $95.70   $95.70  
  Purchase #7 $106.56   9.834%   $117.0391   $117.04   $117.05   $117.00  
  7 purchase totals = $870.18       $951.9195   $951.94   $951.95   $951.90