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	$112.58	13.573%	$127.8605	$127.86	$127.85	$127.90
Purchase #2	$46.53	8.330%	$50.4059	$50.41	$50.40	$50.40
Purchase #3	$146.26	4.513%	$152.8607	$152.86	$152.85	$152.90
Purchase #4	$139.97	9.766%	$153.6395	$153.64	$153.65	$153.60
Purchase #5	$25.79	10.488%	$28.4949	$28.49	$28.50	$28.50
Purchase #6	$56.65	3.613%	$58.6968	$58.70	$58.70	$58.70
Purchase #7	$122.63	9.186%	$133.8948	$133.89	$133.90	$133.90
7 purchase totals =	$650.41		$705.8531	$705.85	$705.85	$705.90