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	$173.43	5.583%	$183.1126	$183.11	$183.10	$183.10
Purchase #2	$73.69	5.668%	$77.8667	$77.87	$77.85	$77.90
Purchase #3	$195.87	4.592%	$204.8644	$204.86	$204.85	$204.90
Purchase #4	$87.44	3.476%	$90.4794	$90.48	$90.50	$90.50
Purchase #5	$125.28	13.377%	$142.0387	$142.04	$142.05	$142.00
Purchase #6	$35.31	5.277%	$37.1733	$37.17	$37.15	$37.20
Purchase #7	$111.79	7.573%	$120.2559	$120.26	$120.25	$120.30
7 purchase totals =	$802.81		$855.7910	$855.79	$855.75	$855.90