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	$105.63	5.611%	$111.5569	$111.56	$111.55	$111.60
Purchase #2	$122.28	8.832%	$133.0798	$133.08	$133.10	$133.10
Purchase #3	$120.30	9.852%	$132.152	$132.15	$132.15	$132.20
Purchase #4	$230.53	11.766%	$257.6542	$257.65	$257.65	$257.70
Purchase #5	$33.63	4.282%	$35.07	$35.07	$35.05	$35.10
Purchase #6	$147.33	10.219%	$162.3857	$162.39	$162.40	$162.40
Purchase #7	$92.32	8.616%	$100.2743	$100.27	$100.25	$100.30
7 purchase totals =	$852.02		$932.1729	$932.17	$932.15	$932.40