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	$179.30	9.592%	$196.4985	$196.50	$196.50	$196.50
Purchase #2	$58.93	12.379%	$66.2249	$66.22	$66.20	$66.20
Purchase #3	$124.71	4.721%	$130.5976	$130.60	$130.60	$130.60
Purchase #4	$248.71	8.376%	$269.5419	$269.54	$269.55	$269.50
Purchase #5	$225.99	7.669%	$243.3212	$243.32	$243.30	$243.30
Purchase #6	$98.91	13.147%	$111.9137	$111.91	$111.90	$111.90
Purchase #7	$182.95	3.123%	$188.6635	$188.66	$188.65	$188.70
7 purchase totals =	$1,119.50		$1,206.7613	$1,206.75	$1,206.70	$1,206.70