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	$100.30	10.833%	$111.1655	$111.17	$111.15	$111.20
Purchase #2	$64.56	3.498%	$66.8183	$66.82	$66.80	$66.80
Purchase #3	$45.47	13.280%	$51.5084	$51.51	$51.50	$51.50
Purchase #4	$224.87	5.592%	$237.4447	$237.44	$237.45	$237.40
Purchase #5	$173.73	12.505%	$195.4549	$195.45	$195.45	$195.50
Purchase #6	$181.64	13.552%	$206.2559	$206.26	$206.25	$206.30
Purchase #7	$199.89	7.169%	$214.2201	$214.22	$214.20	$214.20
7 purchase totals =	$990.46		$1,082.8678	$1,082.87	$1,082.80	$1,082.90