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	$105.60	5.332%	$111.2306	$111.23	$111.25	$111.20
Purchase #2	$172.58	5.482%	$182.0408	$182.04	$182.05	$182.00
Purchase #3	$41.51	4.240%	$43.27	$43.27	$43.25	$43.30
Purchase #4	$149.80	11.547%	$167.0974	$167.10	$167.10	$167.10
Purchase #5	$222.88	6.850%	$238.1473	$238.15	$238.15	$238.10
Purchase #6	$238.85	10.720%	$264.4547	$264.45	$264.45	$264.50
Purchase #7	$137.25	5.808%	$145.2215	$145.22	$145.20	$145.20
7 purchase totals =	$1,068.47		$1,151.4623	$1,151.46	$1,151.45	$1,151.40