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	$193.33	9.568%	$211.8278	$211.83	$211.85	$211.80
Purchase #2	$122.74	6.539%	$130.766	$130.77	$130.75	$130.80
Purchase #3	$173.73	8.152%	$187.8925	$187.89	$187.90	$187.90
Purchase #4	$238.69	13.699%	$271.3881	$271.39	$271.40	$271.40
Purchase #5	$175.35	3.667%	$181.7801	$181.78	$181.80	$181.80
Purchase #6	$156.75	10.284%	$172.8702	$172.87	$172.85	$172.90
Purchase #7	$93.42	12.728%	$105.3105	$105.31	$105.30	$105.30
7 purchase totals =	$1,154.01		$1,261.8352	$1,261.84	$1,261.85	$1,261.90