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	$33.88	4.547%	$35.4205	$35.42	$35.40	$35.40
Purchase #2	$111.70	13.765%	$127.0755	$127.08	$127.10	$127.10
Purchase #3	$13.28	3.671%	$13.7675	$13.77	$13.75	$13.80
Purchase #4	$59.64	3.125%	$61.5038	$61.50	$61.50	$61.50
Purchase #5	$12.56	11.583%	$14.0148	$14.01	$14.00	$14.00
Purchase #6	$141.58	6.843%	$151.2683	$151.27	$151.25	$151.30
Purchase #7	$35.65	10.260%	$39.3077	$39.31	$39.30	$39.30
7 purchase totals =	$408.29		$442.3581	$442.36	$442.30	$442.40