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 $174.85   12.275%   $196.3128   $196.31   $196.30   $196.30  
  Purchase #2 $178.88   9.383%   $195.6643   $195.66   $195.65   $195.70  
  Purchase #3 $65.98   10.540%   $72.9343   $72.93   $72.95   $72.90  
  Purchase #4 $17.98   10.706%   $19.9049   $19.90   $19.90   $19.90  
  Purchase #5 $22.98   5.297%   $24.1973   $24.20   $24.20   $24.20  
  Purchase #6 $48.27   5.389%   $50.8713   $50.87   $50.85   $50.90  
  Purchase #7 $164.43   7.690%   $177.0747   $177.07   $177.05   $177.10  
  7 purchase totals = $673.37       $736.9596   $736.94   $736.90   $737.00