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	$227.73	4.787%	$238.6314	$238.63	$238.65	$238.60
Purchase #2	$10.34	13.853%	$11.7724	$11.77	$11.75	$11.80
Purchase #3	$173.99	8.524%	$188.8209	$188.82	$188.80	$188.80
Purchase #4	$70.89	4.612%	$74.1594	$74.16	$74.15	$74.20
Purchase #5	$230.33	12.309%	$258.6813	$258.68	$258.70	$258.70
Purchase #6	$109.34	6.367%	$116.3017	$116.30	$116.30	$116.30
Purchase #7	$165.46	4.441%	$172.8081	$172.81	$172.80	$172.80
7 purchase totals =	$988.08		$1,061.1752	$1,061.17	$1,061.15	$1,061.20