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	$229.78	10.603%	$254.1436	$254.14	$254.15	$254.10
Purchase #2	$242.56	13.488%	$275.2765	$275.28	$275.30	$275.30
Purchase #3	$12.27	3.773%	$12.7329	$12.73	$12.75	$12.70
Purchase #4	$142.51	11.456%	$158.8359	$158.84	$158.85	$158.80
Purchase #5	$229.38	13.256%	$259.7866	$259.79	$259.80	$259.80
Purchase #6	$171.98	5.763%	$181.8912	$181.89	$181.90	$181.90
Purchase #7	$100.27	10.339%	$110.6369	$110.64	$110.65	$110.60
7 purchase totals =	$1,128.75		$1,253.3036	$1,253.31	$1,253.40	$1,253.20