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	$230.95	13.801%	$262.8234	$262.82	$262.80	$262.80
Purchase #2	$226.92	12.172%	$254.5407	$254.54	$254.55	$254.50
Purchase #3	$15.64	12.111%	$17.5342	$17.53	$17.55	$17.50
Purchase #4	$12.77	13.202%	$14.4559	$14.46	$14.45	$14.50
Purchase #5	$178.52	12.167%	$200.2405	$200.24	$200.25	$200.20
Purchase #6	$53.39	11.323%	$59.4353	$59.44	$59.45	$59.40
Purchase #7	$121.79	12.654%	$137.2013	$137.20	$137.20	$137.20
7 purchase totals =	$839.98		$946.2313	$946.23	$946.25	$946.10