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	$230.72	4.504%	$241.1116	$241.11	$241.10	$241.10
Purchase #2	$111.90	13.544%	$127.0557	$127.06	$127.05	$127.10
Purchase #3	$147.72	10.407%	$163.0932	$163.09	$163.10	$163.10
Purchase #4	$54.58	4.334%	$56.9455	$56.95	$56.95	$56.90
Purchase #5	$93.35	9.552%	$102.2668	$102.27	$102.25	$102.30
Purchase #6	$45.42	13.349%	$51.4831	$51.48	$51.50	$51.50
Purchase #7	$174.95	12.128%	$196.1679	$196.17	$196.15	$196.20
7 purchase totals =	$858.64		$938.1238	$938.13	$938.10	$938.20