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	$226.76	11.259%	$252.2909	$252.29	$252.30	$252.30
Purchase #2	$81.29	6.528%	$86.5966	$86.60	$86.60	$86.60
Purchase #3	$196.31	7.562%	$211.155	$211.16	$211.15	$211.20
Purchase #4	$119.90	6.621%	$127.8386	$127.84	$127.85	$127.80
Purchase #5	$10.94	12.673%	$12.3264	$12.33	$12.35	$12.30
Purchase #6	$70.54	13.304%	$79.9246	$79.92	$79.90	$79.90
Purchase #7	$75.30	4.351%	$78.5763	$78.58	$78.60	$78.60
7 purchase totals =	$781.04		$848.7084	$848.72	$848.75	$848.70