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	$222.62	9.184%	$243.0654	$243.07	$243.05	$243.10
Purchase #2	$98.29	13.599%	$111.6565	$111.66	$111.65	$111.70
Purchase #3	$169.52	9.859%	$186.233	$186.23	$186.25	$186.20
Purchase #4	$19.66	8.130%	$21.2584	$21.26	$21.25	$21.30
Purchase #5	$223.69	7.554%	$240.5875	$240.59	$240.60	$240.60
Purchase #6	$204.82	5.520%	$216.1261	$216.13	$216.15	$216.10
Purchase #7	$70.98	4.739%	$74.3437	$74.34	$74.35	$74.30
7 purchase totals =	$1,009.58		$1,093.2706	$1,093.28	$1,093.30	$1,093.30