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	$53.51	10.792%	$59.2848	$59.28	$59.30	$59.30
Purchase #2	$144.78	11.623%	$161.6078	$161.61	$161.60	$161.60
Purchase #3	$135.77	4.640%	$142.0697	$142.07	$142.05	$142.10
Purchase #4	$149.75	6.813%	$159.9525	$159.95	$159.95	$160.00
Purchase #5	$177.95	5.794%	$188.2604	$188.26	$188.25	$188.30
Purchase #6	$193.68	13.129%	$219.1082	$219.11	$219.10	$219.10
Purchase #7	$120.80	8.584%	$131.1695	$131.17	$131.15	$131.20
7 purchase totals =	$976.24		$1,061.4529	$1,061.45	$1,061.40	$1,061.60