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	$145.77	7.388%	$156.5395	$156.54	$156.55	$156.50
Purchase #2	$217.42	8.158%	$235.1571	$235.16	$235.15	$235.20
Purchase #3	$126.26	11.814%	$141.1764	$141.18	$141.20	$141.20
Purchase #4	$186.44	9.147%	$203.4937	$203.49	$203.50	$203.50
Purchase #5	$55.61	10.763%	$61.5953	$61.60	$61.60	$61.60
Purchase #6	$122.51	12.558%	$137.8948	$137.89	$137.90	$137.90
Purchase #7	$11.89	5.642%	$12.5608	$12.56	$12.55	$12.60
7 purchase totals =	$865.90		$948.4176	$948.42	$948.45	$948.50