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	$248.58	12.149%	$278.78	$278.78	$278.80	$278.80
Purchase #2	$82.65	8.392%	$89.586	$89.59	$89.60	$89.60
Purchase #3	$171.56	6.763%	$183.1626	$183.16	$183.15	$183.20
Purchase #4	$97.53	13.869%	$111.0564	$111.06	$111.05	$111.10
Purchase #5	$61.55	13.298%	$69.7349	$69.73	$69.75	$69.70
Purchase #6	$136.33	7.241%	$146.2017	$146.20	$146.20	$146.20
Purchase #7	$161.27	7.824%	$173.8878	$173.89	$173.90	$173.90
7 purchase totals =	$959.47		$1,052.4094	$1,052.41	$1,052.45	$1,052.50