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	$244.34	3.391%	$252.6256	$252.63	$252.65	$252.60
Purchase #2	$54.64	9.408%	$59.7805	$59.78	$59.80	$59.80
Purchase #3	$139.36	5.384%	$146.8631	$146.86	$146.85	$146.90
Purchase #4	$159.78	8.565%	$173.4652	$173.47	$173.45	$173.50
Purchase #5	$130.89	10.783%	$145.0039	$145.00	$145.00	$145.00
Purchase #6	$80.83	5.365%	$85.1665	$85.17	$85.15	$85.20
Purchase #7	$76.65	11.299%	$85.3107	$85.31	$85.30	$85.30
7 purchase totals =	$886.49		$948.2155	$948.22	$948.20	$948.30