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	$116.61	5.363%	$122.8638	$122.86	$122.85	$122.90
Purchase #2	$45.45	7.163%	$48.7056	$48.71	$48.70	$48.70
Purchase #3	$103.98	13.714%	$118.2398	$118.24	$118.25	$118.20
Purchase #4	$159.72	3.528%	$165.3549	$165.35	$165.35	$165.40
Purchase #5	$133.45	9.785%	$146.5081	$146.51	$146.50	$146.50
Purchase #6	$141.38	11.223%	$157.2471	$157.25	$157.25	$157.20
Purchase #7	$52.54	5.861%	$55.6194	$55.62	$55.60	$55.60
7 purchase totals =	$753.13		$814.5387	$814.54	$814.50	$814.50