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	$153.79	13.126%	$173.9765	$173.98	$174.00	$174.00
Purchase #2	$48.47	3.862%	$50.3419	$50.34	$50.35	$50.30
Purchase #3	$111.28	6.241%	$118.225	$118.23	$118.25	$118.20
Purchase #4	$112.52	9.629%	$123.3546	$123.35	$123.35	$123.40
Purchase #5	$230.66	5.825%	$244.0959	$244.10	$244.10	$244.10
Purchase #6	$79.78	12.260%	$89.561	$89.56	$89.55	$89.60
Purchase #7	$135.50	11.760%	$151.4348	$151.43	$151.45	$151.40
7 purchase totals =	$872.00		$950.9897	$950.99	$951.05	$951.00