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	$68.69	3.738%	$71.2576	$71.26	$71.25	$71.30
Purchase #2	$158.46	11.103%	$176.0538	$176.05	$176.05	$176.10
Purchase #3	$48.98	3.259%	$50.5763	$50.58	$50.60	$50.60
Purchase #4	$249.81	4.213%	$260.3345	$260.33	$260.35	$260.30
Purchase #5	$91.96	13.614%	$104.4794	$104.48	$104.50	$104.50
Purchase #6	$237.87	5.643%	$251.293	$251.29	$251.30	$251.30
Purchase #7	$225.90	5.437%	$238.1822	$238.18	$238.20	$238.20
7 purchase totals =	$1,081.67		$1,152.1768	$1,152.17	$1,152.25	$1,152.30