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	$160.51	4.457%	$167.6639	$167.66	$167.65	$167.70
Purchase #2	$61.50	5.802%	$65.0682	$65.07	$65.05	$65.10
Purchase #3	$92.31	3.256%	$95.3156	$95.32	$95.30	$95.30
Purchase #4	$34.45	6.343%	$36.6352	$36.64	$36.65	$36.60
Purchase #5	$54.51	4.534%	$56.9815	$56.98	$57.00	$57.00
Purchase #6	$9.87	4.634%	$10.3274	$10.33	$10.35	$10.30
Purchase #7	$157.42	5.689%	$166.3756	$166.38	$166.40	$166.40
7 purchase totals =	$570.57		$598.3674	$598.38	$598.40	$598.40