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	$107.31	3.625%	$111.2	$111.20	$111.20	$111.20
Purchase #2	$150.52	5.621%	$158.9807	$158.98	$159.00	$159.00
Purchase #3	$158.43	10.737%	$175.4406	$175.44	$175.45	$175.40
Purchase #4	$58.41	6.864%	$62.4193	$62.42	$62.40	$62.40
Purchase #5	$248.82	10.161%	$274.1026	$274.10	$274.10	$274.10
Purchase #6	$230.71	10.228%	$254.307	$254.31	$254.30	$254.30
Purchase #7	$28.89	12.630%	$32.5388	$32.54	$32.55	$32.50
7 purchase totals =	$983.09		$1,068.9890	$1,068.99	$1,069.00	$1,068.90