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	$165.69	9.180%	$180.9003	$180.90	$180.90	$180.90
Purchase #2	$68.85	7.297%	$73.874	$73.87	$73.85	$73.90
Purchase #3	$20.65	3.569%	$21.387	$21.39	$21.40	$21.40
Purchase #4	$74.83	5.149%	$78.683	$78.68	$78.70	$78.70
Purchase #5	$235.31	8.573%	$255.4831	$255.48	$255.50	$255.50
Purchase #6	$107.64	12.517%	$121.1133	$121.11	$121.10	$121.10
Purchase #7	$29.49	13.776%	$33.5525	$33.55	$33.55	$33.60
7 purchase totals =	$702.46		$764.9932	$764.98	$765.00	$765.10