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	$62.58	3.271%	$64.627	$64.63	$64.65	$64.60
Purchase #2	$209.89	6.770%	$224.0996	$224.10	$224.10	$224.10
Purchase #3	$138.37	9.775%	$151.8957	$151.90	$151.90	$151.90
Purchase #4	$91.62	6.357%	$97.4443	$97.44	$97.45	$97.40
Purchase #5	$196.82	13.519%	$223.4281	$223.43	$223.45	$223.40
Purchase #6	$131.78	4.169%	$137.2739	$137.27	$137.25	$137.30
Purchase #7	$75.50	3.463%	$78.1146	$78.11	$78.10	$78.10
7 purchase totals =	$906.56		$976.8832	$976.88	$976.90	$976.80