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	$55.68	12.591%	$62.6907	$62.69	$62.70	$62.70
Purchase #2	$121.30	4.784%	$127.103	$127.10	$127.10	$127.10
Purchase #3	$188.32	13.754%	$214.2215	$214.22	$214.20	$214.20
Purchase #4	$58.81	11.861%	$65.7855	$65.79	$65.80	$65.80
Purchase #5	$190.30	8.512%	$206.4983	$206.50	$206.50	$206.50
Purchase #6	$80.54	5.829%	$85.2347	$85.23	$85.25	$85.20
Purchase #7	$11.60	10.353%	$12.8009	$12.80	$12.80	$12.80
7 purchase totals =	$706.55		$774.3346	$774.33	$774.35	$774.30