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 $90.83   5.834%   $96.129   $96.13   $96.15   $96.10  
  Purchase #2 $45.69   4.384%   $47.693   $47.69   $47.70   $47.70  
  Purchase #3 $34.67   12.355%   $38.9535   $38.95   $38.95   $39.00  
  Purchase #4 $87.52   11.395%   $97.4929   $97.49   $97.50   $97.50  
  Purchase #5 $57.52   10.627%   $63.6327   $63.63   $63.65   $63.60  
  Purchase #6 $188.72   13.292%   $213.8047   $213.80   $213.80   $213.80  
  Purchase #7 $214.66   10.103%   $236.3471   $236.35   $236.35   $236.30  
  7 purchase totals = $719.61       $794.0529   $794.04   $794.10   $794.00