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	$61.71	8.229%	$66.7881	$66.79	$66.80	$66.80
Purchase #2	$187.86	12.116%	$210.6211	$210.62	$210.60	$210.60
Purchase #3	$152.33	13.380%	$172.7118	$172.71	$172.70	$172.70
Purchase #4	$136.67	6.505%	$145.5604	$145.56	$145.55	$145.60
Purchase #5	$236.70	12.251%	$265.6981	$265.70	$265.70	$265.70
Purchase #6	$221.77	3.852%	$230.3126	$230.31	$230.30	$230.30
Purchase #7	$149.48	8.780%	$162.6043	$162.60	$162.60	$162.60
7 purchase totals =	$1,146.52		$1,254.2964	$1,254.29	$1,254.25	$1,254.30