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	$159.54	10.213%	$175.8338	$175.83	$175.85	$175.80
Purchase #2	$46.83	8.348%	$50.7394	$50.74	$50.75	$50.70
Purchase #3	$64.35	11.792%	$71.9382	$71.94	$71.95	$71.90
Purchase #4	$177.59	4.500%	$185.5816	$185.58	$185.60	$185.60
Purchase #5	$245.96	7.668%	$264.8202	$264.82	$264.80	$264.80
Purchase #6	$44.50	11.237%	$49.5005	$49.50	$49.50	$49.50
Purchase #7	$153.42	5.501%	$161.8596	$161.86	$161.85	$161.90
7 purchase totals =	$892.19		$960.2733	$960.27	$960.30	$960.20