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	$144.44	10.499%	$159.6048	$159.60	$159.60	$159.60
Purchase #2	$54.27	13.468%	$61.5791	$61.58	$61.60	$61.60
Purchase #3	$82.34	13.455%	$93.4188	$93.42	$93.40	$93.40
Purchase #4	$173.34	12.401%	$194.8359	$194.84	$194.85	$194.80
Purchase #5	$139.83	11.840%	$156.3859	$156.39	$156.40	$156.40
Purchase #6	$230.35	11.195%	$256.1377	$256.14	$256.15	$256.10
Purchase #7	$93.35	7.191%	$100.0628	$100.06	$100.05	$100.10
7 purchase totals =	$917.92		$1,022.0250	$1,022.03	$1,022.05	$1,022.00