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	$149.58	7.655%	$161.0303	$161.03	$161.05	$161.00
Purchase #2	$154.70	11.664%	$172.7442	$172.74	$172.75	$172.70
Purchase #3	$11.36	13.122%	$12.8507	$12.85	$12.85	$12.90
Purchase #4	$245.59	13.169%	$277.9317	$277.93	$277.95	$277.90
Purchase #5	$50.35	9.363%	$55.0643	$55.06	$55.05	$55.10
Purchase #6	$111.72	4.328%	$116.5552	$116.56	$116.55	$116.60
Purchase #7	$74.38	5.233%	$78.2723	$78.27	$78.25	$78.30
7 purchase totals =	$797.68		$874.4487	$874.44	$874.45	$874.50