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	$229.69	3.713%	$238.2184	$238.22	$238.20	$238.20
Purchase #2	$11.81	13.322%	$13.3833	$13.38	$13.40	$13.40
Purchase #3	$60.81	11.301%	$67.6821	$67.68	$67.70	$67.70
Purchase #4	$47.28	11.779%	$52.8491	$52.85	$52.85	$52.80
Purchase #5	$168.92	7.456%	$181.5147	$181.51	$181.50	$181.50
Purchase #6	$240.27	12.856%	$271.1591	$271.16	$271.15	$271.20
Purchase #7	$64.25	3.823%	$66.7063	$66.71	$66.70	$66.70
7 purchase totals =	$823.03		$891.5130	$891.51	$891.50	$891.50