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	$44.68	3.369%	$46.1853	$46.19	$46.20	$46.20
Purchase #2	$86.95	4.152%	$90.5602	$90.56	$90.55	$90.60
Purchase #3	$211.46	6.669%	$225.5623	$225.56	$225.55	$225.60
Purchase #4	$121.57	6.364%	$129.3067	$129.31	$129.30	$129.30
Purchase #5	$129.44	13.144%	$146.4536	$146.45	$146.45	$146.50
Purchase #6	$49.97	9.160%	$54.5473	$54.55	$54.55	$54.50
Purchase #7	$242.81	6.573%	$258.7699	$258.77	$258.75	$258.80
7 purchase totals =	$886.88		$951.3853	$951.39	$951.35	$951.50