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	$154.62	6.211%	$164.2234	$164.22	$164.20	$164.20
Purchase #2	$230.67	12.286%	$259.0101	$259.01	$259.00	$259.00
Purchase #3	$47.92	9.505%	$52.4748	$52.47	$52.45	$52.50
Purchase #4	$161.76	8.420%	$175.3802	$175.38	$175.40	$175.40
Purchase #5	$104.94	3.439%	$108.5489	$108.55	$108.55	$108.50
Purchase #6	$111.91	13.803%	$127.3569	$127.36	$127.35	$127.40
Purchase #7	$195.75	4.846%	$205.236	$205.24	$205.25	$205.20
7 purchase totals =	$1,007.57		$1,092.2303	$1,092.23	$1,092.20	$1,092.20