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	$43.90	11.475%	$48.9375	$48.94	$48.95	$48.90
Purchase #2	$184.48	4.681%	$193.1155	$193.12	$193.10	$193.10
Purchase #3	$154.58	13.256%	$175.0711	$175.07	$175.05	$175.10
Purchase #4	$146.69	3.469%	$151.7787	$151.78	$151.80	$151.80
Purchase #5	$204.52	13.657%	$232.4513	$232.45	$232.45	$232.50
Purchase #6	$122.89	13.337%	$139.2798	$139.28	$139.30	$139.30
Purchase #7	$209.55	10.463%	$231.4752	$231.48	$231.50	$231.50
7 purchase totals =	$1,066.61		$1,172.1091	$1,172.12	$1,172.15	$1,172.20