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	$190.53	8.480%	$206.6869	$206.69	$206.70	$206.70
Purchase #2	$9.83	9.695%	$10.783	$10.78	$10.80	$10.80
Purchase #3	$116.35	11.845%	$130.1317	$130.13	$130.15	$130.10
Purchase #4	$96.26	9.709%	$105.6059	$105.61	$105.60	$105.60
Purchase #5	$133.83	13.776%	$152.2664	$152.27	$152.25	$152.30
Purchase #6	$148.59	4.364%	$155.0745	$155.07	$155.05	$155.10
Purchase #7	$86.81	4.272%	$90.5185	$90.52	$90.50	$90.50
7 purchase totals =	$782.20		$851.0669	$851.07	$851.05	$851.10