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	$226.89	11.179%	$252.254	$252.25	$252.25	$252.30
Purchase #2	$108.52	13.374%	$123.0335	$123.03	$123.05	$123.00
Purchase #3	$58.75	4.411%	$61.3415	$61.34	$61.35	$61.30
Purchase #4	$153.69	5.224%	$161.7188	$161.72	$161.70	$161.70
Purchase #5	$46.59	13.636%	$52.943	$52.94	$52.95	$52.90
Purchase #6	$32.91	13.702%	$37.4193	$37.42	$37.40	$37.40
Purchase #7	$146.85	8.766%	$159.7229	$159.72	$159.70	$159.70
7 purchase totals =	$774.20		$848.4330	$848.42	$848.40	$848.30