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	$138.33	4.351%	$144.3487	$144.35	$144.35	$144.30
Purchase #2	$33.45	12.650%	$37.6814	$37.68	$37.70	$37.70
Purchase #3	$15.29	13.310%	$17.3251	$17.33	$17.35	$17.30
Purchase #4	$105.85	3.207%	$109.2446	$109.24	$109.25	$109.20
Purchase #5	$22.50	5.420%	$23.7195	$23.72	$23.70	$23.70
Purchase #6	$54.79	9.118%	$59.7858	$59.79	$59.80	$59.80
Purchase #7	$131.73	7.106%	$141.0907	$141.09	$141.10	$141.10
7 purchase totals =	$501.94		$533.1958	$533.20	$533.25	$533.10