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	$228.25	8.505%	$247.6627	$247.66	$247.65	$247.70
Purchase #2	$245.92	13.266%	$278.5437	$278.54	$278.55	$278.50
Purchase #3	$124.34	10.664%	$137.5996	$137.60	$137.60	$137.60
Purchase #4	$121.72	5.393%	$128.2844	$128.28	$128.30	$128.30
Purchase #5	$160.35	13.649%	$182.2362	$182.24	$182.25	$182.20
Purchase #6	$37.33	12.567%	$42.0213	$42.02	$42.00	$42.00
Purchase #7	$100.50	10.860%	$111.4143	$111.41	$111.40	$111.40
7 purchase totals =	$1,018.41		$1,127.7622	$1,127.75	$1,127.75	$1,127.70