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	$30.37	10.288%	$33.4945	$33.49	$33.50	$33.50
Purchase #2	$166.38	5.111%	$174.8837	$174.88	$174.90	$174.90
Purchase #3	$72.41	8.525%	$78.583	$78.58	$78.60	$78.60
Purchase #4	$199.43	3.275%	$205.9613	$205.96	$205.95	$206.00
Purchase #5	$9.78	4.350%	$10.2054	$10.21	$10.20	$10.20
Purchase #6	$116.72	9.389%	$127.6788	$127.68	$127.70	$127.70
Purchase #7	$111.62	10.488%	$123.3267	$123.33	$123.35	$123.30
7 purchase totals =	$706.71		$754.1334	$754.13	$754.20	$754.20