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	$40.31	8.260%	$43.6396	$43.64	$43.65	$43.60
Purchase #2	$106.52	4.270%	$111.0684	$111.07	$111.05	$111.10
Purchase #3	$91.29	10.346%	$100.7349	$100.73	$100.75	$100.70
Purchase #4	$61.42	9.847%	$67.468	$67.47	$67.45	$67.50
Purchase #5	$16.27	6.468%	$17.3223	$17.32	$17.30	$17.30
Purchase #6	$106.60	3.655%	$110.4962	$110.50	$110.50	$110.50
Purchase #7	$31.29	13.227%	$35.4287	$35.43	$35.45	$35.40
7 purchase totals =	$453.70		$486.1581	$486.16	$486.15	$486.10