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	$227.72	4.402%	$237.7442	$237.74	$237.75	$237.70
Purchase #2	$166.52	13.181%	$188.469	$188.47	$188.45	$188.50
Purchase #3	$119.89	7.191%	$128.5113	$128.51	$128.50	$128.50
Purchase #4	$48.52	11.651%	$54.1731	$54.17	$54.15	$54.20
Purchase #5	$143.31	5.729%	$151.5202	$151.52	$151.50	$151.50
Purchase #6	$248.56	8.488%	$269.6578	$269.66	$269.65	$269.70
Purchase #7	$107.48	3.707%	$111.4643	$111.46	$111.45	$111.50
7 purchase totals =	$1,062.00		$1,141.5399	$1,141.53	$1,141.45	$1,141.60