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	$55.95	7.399%	$60.0897	$60.09	$60.10	$60.10
Purchase #2	$116.32	13.452%	$131.9674	$131.97	$131.95	$132.00
Purchase #3	$71.38	9.458%	$78.1311	$78.13	$78.15	$78.10
Purchase #4	$21.50	6.784%	$22.9586	$22.96	$22.95	$23.00
Purchase #5	$179.29	6.314%	$190.6104	$190.61	$190.60	$190.60
Purchase #6	$103.45	4.502%	$108.1073	$108.11	$108.10	$108.10
Purchase #7	$138.78	4.795%	$145.4345	$145.43	$145.45	$145.40
7 purchase totals =	$686.67		$737.2990	$737.30	$737.30	$737.30