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	$152.45	11.387%	$169.8095	$169.81	$169.80	$169.80
Purchase #2	$105.37	5.613%	$111.2844	$111.28	$111.30	$111.30
Purchase #3	$100.94	10.819%	$111.8607	$111.86	$111.85	$111.90
Purchase #4	$100.86	9.367%	$110.3076	$110.31	$110.30	$110.30
Purchase #5	$69.95	13.382%	$79.3107	$79.31	$79.30	$79.30
Purchase #6	$96.27	10.536%	$106.413	$106.41	$106.40	$106.40
Purchase #7	$37.62	13.300%	$42.6235	$42.62	$42.60	$42.60
7 purchase totals =	$663.46		$731.6094	$731.60	$731.55	$731.60