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	$162.81	10.251%	$179.4997	$179.50	$179.50	$179.50
Purchase #2	$157.30	10.402%	$173.6623	$173.66	$173.65	$173.70
Purchase #3	$243.58	4.310%	$254.0783	$254.08	$254.10	$254.10
Purchase #4	$116.45	7.140%	$124.7645	$124.76	$124.75	$124.80
Purchase #5	$47.50	10.544%	$52.5084	$52.51	$52.50	$52.50
Purchase #6	$139.70	13.301%	$158.2815	$158.28	$158.30	$158.30
Purchase #7	$136.70	4.211%	$142.4564	$142.46	$142.45	$142.50
7 purchase totals =	$1,004.04		$1,085.2511	$1,085.25	$1,085.25	$1,085.40