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	$202.54	13.858%	$230.608	$230.61	$230.60	$230.60
Purchase #2	$245.74	8.521%	$266.6795	$266.68	$266.70	$266.70
Purchase #3	$40.72	4.426%	$42.5223	$42.52	$42.50	$42.50
Purchase #4	$156.53	7.547%	$168.3433	$168.34	$168.35	$168.30
Purchase #5	$48.35	10.529%	$53.4408	$53.44	$53.45	$53.40
Purchase #6	$143.86	3.299%	$148.6059	$148.61	$148.60	$148.60
Purchase #7	$157.66	6.702%	$168.2264	$168.23	$168.25	$168.20
7 purchase totals =	$995.40		$1,078.4262	$1,078.43	$1,078.45	$1,078.30