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	$34.29	3.608%	$35.5272	$35.53	$35.55	$35.50
Purchase #2	$143.86	12.194%	$161.4023	$161.40	$161.40	$161.40
Purchase #3	$231.25	5.224%	$243.3305	$243.33	$243.35	$243.30
Purchase #4	$105.28	6.198%	$111.8053	$111.81	$111.80	$111.80
Purchase #5	$173.79	3.829%	$180.4444	$180.44	$180.45	$180.40
Purchase #6	$141.84	8.211%	$153.4865	$153.49	$153.50	$153.50
Purchase #7	$117.31	11.460%	$130.7537	$130.75	$130.75	$130.80
7 purchase totals =	$947.62		$1,016.7499	$1,016.75	$1,016.80	$1,016.70