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	$115.55	12.721%	$130.2491	$130.25	$130.25	$130.20
Purchase #2	$18.82	9.616%	$20.6297	$20.63	$20.65	$20.60
Purchase #3	$112.61	4.659%	$117.8565	$117.86	$117.85	$117.90
Purchase #4	$109.78	6.248%	$116.6391	$116.64	$116.65	$116.60
Purchase #5	$173.82	6.366%	$184.8854	$184.89	$184.90	$184.90
Purchase #6	$70.77	11.469%	$78.8866	$78.89	$78.90	$78.90
Purchase #7	$56.81	5.609%	$59.9965	$60.00	$60.00	$60.00
7 purchase totals =	$658.16		$709.1429	$709.16	$709.20	$709.10