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	$100.39	11.191%	$111.6246	$111.62	$111.60	$111.60
Purchase #2	$212.45	3.483%	$219.8496	$219.85	$219.85	$219.80
Purchase #3	$153.42	8.758%	$166.8565	$166.86	$166.85	$166.90
Purchase #4	$76.58	5.313%	$80.6487	$80.65	$80.65	$80.60
Purchase #5	$41.90	13.652%	$47.6202	$47.62	$47.60	$47.60
Purchase #6	$226.36	12.459%	$254.5622	$254.56	$254.55	$254.60
Purchase #7	$92.93	8.135%	$100.4899	$100.49	$100.50	$100.50
7 purchase totals =	$904.03		$981.6517	$981.65	$981.60	$981.60