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	$204.58	9.760%	$224.547	$224.55	$224.55	$224.50
Purchase #2	$12.25	9.583%	$13.4239	$13.42	$13.40	$13.40
Purchase #3	$124.45	6.636%	$132.7085	$132.71	$132.70	$132.70
Purchase #4	$60.54	10.498%	$66.8955	$66.90	$66.90	$66.90
Purchase #5	$85.27	3.565%	$88.3099	$88.31	$88.30	$88.30
Purchase #6	$55.60	7.636%	$59.8456	$59.85	$59.85	$59.80
Purchase #7	$21.34	6.333%	$22.6915	$22.69	$22.70	$22.70
7 purchase totals =	$564.03		$608.4219	$608.43	$608.40	$608.30