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	$93.69	12.703%	$105.5914	$105.59	$105.60	$105.60
Purchase #2	$242.70	4.437%	$253.4686	$253.47	$253.45	$253.50
Purchase #3	$135.91	12.196%	$152.4856	$152.49	$152.50	$152.50
Purchase #4	$24.48	11.233%	$27.2298	$27.23	$27.25	$27.20
Purchase #5	$88.33	7.802%	$95.2215	$95.22	$95.20	$95.20
Purchase #6	$159.30	8.106%	$172.2129	$172.21	$172.20	$172.20
Purchase #7	$230.86	3.594%	$239.1571	$239.16	$239.15	$239.20
7 purchase totals =	$975.27		$1,045.3669	$1,045.37	$1,045.35	$1,045.40