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	$209.50	6.178%	$222.4429	$222.44	$222.45	$222.40
Purchase #2	$209.56	6.140%	$222.427	$222.43	$222.45	$222.40
Purchase #3	$98.25	13.858%	$111.8655	$111.87	$111.85	$111.90
Purchase #4	$29.68	13.781%	$33.7702	$33.77	$33.75	$33.80
Purchase #5	$233.47	9.403%	$255.4232	$255.42	$255.40	$255.40
Purchase #6	$186.57	9.727%	$204.7177	$204.72	$204.70	$204.70
Purchase #7	$243.90	6.162%	$258.9291	$258.93	$258.95	$258.90
7 purchase totals =	$1,210.93		$1,309.5756	$1,309.58	$1,309.55	$1,309.50