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	$206.65	13.842%	$235.2545	$235.25	$235.25	$235.30
Purchase #2	$214.72	6.874%	$229.4799	$229.48	$229.50	$229.50
Purchase #3	$65.72	6.590%	$70.0509	$70.05	$70.05	$70.10
Purchase #4	$138.87	5.651%	$146.7175	$146.72	$146.70	$146.70
Purchase #5	$111.73	13.186%	$126.4627	$126.46	$126.45	$126.50
Purchase #6	$191.80	12.662%	$216.0857	$216.09	$216.10	$216.10
Purchase #7	$72.85	7.504%	$78.3167	$78.32	$78.30	$78.30
7 purchase totals =	$1,002.34		$1,102.3679	$1,102.37	$1,102.35	$1,102.50