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	$150.55	12.301%	$169.0692	$169.07	$169.05	$169.10
Purchase #2	$34.63	12.317%	$38.8954	$38.90	$38.90	$38.90
Purchase #3	$92.42	10.150%	$101.8006	$101.80	$101.80	$101.80
Purchase #4	$98.27	13.707%	$111.7399	$111.74	$111.75	$111.70
Purchase #5	$27.92	4.388%	$29.1451	$29.15	$29.15	$29.10
Purchase #6	$222.56	3.843%	$231.113	$231.11	$231.10	$231.10
Purchase #7	$166.30	10.393%	$183.5836	$183.58	$183.60	$183.60
7 purchase totals =	$792.65		$865.3468	$865.35	$865.35	$865.30