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 $114.29   3.694%   $118.5119   $118.51   $118.50   $118.50  
  Purchase #2 $54.67   10.414%   $60.3633   $60.36   $60.35   $60.40  
  Purchase #3 $115.54   13.828%   $131.5169   $131.52   $131.50   $131.50  
  Purchase #4 $231.29   5.255%   $243.4443   $243.44   $243.45   $243.40  
  Purchase #5 $10.39   7.164%   $11.1343   $11.13   $11.15   $11.10  
  Purchase #6 $117.87   7.235%   $126.3979   $126.40   $126.40   $126.40  
  Purchase #7 $244.73   10.613%   $270.7032   $270.70   $270.70   $270.70  
  7 purchase totals = $888.78       $962.0718   $962.06   $962.05   $962.00