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 $174.97   10.659%   $193.6201   $193.62   $193.60   $193.60  
  Purchase #2 $80.49   3.361%   $83.1953   $83.20   $83.20   $83.20  
  Purchase #3 $86.51   3.650%   $89.6676   $89.67   $89.65   $89.70  
  Purchase #4 $86.42   9.420%   $94.5608   $94.56   $94.55   $94.60  
  Purchase #5 $68.41   3.768%   $70.9877   $70.99   $71.00   $71.00  
  Purchase #6 $204.49   8.307%   $221.477   $221.48   $221.50   $221.50  
  Purchase #7 $183.49   3.407%   $189.7415   $189.74   $189.75   $189.70  
  7 purchase totals = $884.78       $943.2500   $943.26   $943.25   $943.30