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	$185.56	10.214%	$204.5131	$204.51	$204.50	$204.50
Purchase #2	$145.59	5.494%	$153.5887	$153.59	$153.60	$153.60
Purchase #3	$107.48	3.345%	$111.0752	$111.08	$111.10	$111.10
Purchase #4	$220.75	3.341%	$228.1253	$228.13	$228.15	$228.10
Purchase #5	$228.28	6.678%	$243.5245	$243.52	$243.50	$243.50
Purchase #6	$213.93	7.573%	$230.1309	$230.13	$230.15	$230.10
Purchase #7	$143.83	4.479%	$150.2721	$150.27	$150.25	$150.30
7 purchase totals =	$1,245.42		$1,321.2298	$1,321.23	$1,321.25	$1,321.20