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	$212.29	13.555%	$241.0659	$241.07	$241.05	$241.10
Purchase #2	$37.95	12.208%	$42.5829	$42.58	$42.60	$42.60
Purchase #3	$209.46	12.145%	$234.8989	$234.90	$234.90	$234.90
Purchase #4	$28.58	13.729%	$32.5037	$32.50	$32.50	$32.50
Purchase #5	$30.39	6.610%	$32.3988	$32.40	$32.40	$32.40
Purchase #6	$22.95	6.585%	$24.4613	$24.46	$24.45	$24.50
Purchase #7	$99.88	7.176%	$107.0474	$107.05	$107.05	$107.00
7 purchase totals =	$641.50		$714.9589	$714.96	$714.95	$715.00