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	$126.58	3.740%	$131.3141	$131.31	$131.30	$131.30
Purchase #2	$174.92	4.318%	$182.473	$182.47	$182.45	$182.50
Purchase #3	$17.92	13.135%	$20.2738	$20.27	$20.25	$20.30
Purchase #4	$48.43	13.453%	$54.9453	$54.95	$54.95	$54.90
Purchase #5	$35.90	10.458%	$39.6544	$39.65	$39.65	$39.70
Purchase #6	$60.82	11.721%	$67.9487	$67.95	$67.95	$67.90
Purchase #7	$203.36	13.422%	$230.655	$230.66	$230.65	$230.70
7 purchase totals =	$667.93		$727.2643	$727.26	$727.20	$727.30