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	$217.78	11.406%	$242.62	$242.62	$242.60	$242.60
Purchase #2	$67.31	5.640%	$71.1063	$71.11	$71.10	$71.10
Purchase #3	$238.62	13.491%	$270.8122	$270.81	$270.80	$270.80
Purchase #4	$14.95	10.129%	$16.4643	$16.46	$16.45	$16.50
Purchase #5	$214.39	4.208%	$223.4115	$223.41	$223.40	$223.40
Purchase #6	$32.97	12.412%	$37.0622	$37.06	$37.05	$37.10
Purchase #7	$181.39	7.438%	$194.8818	$194.88	$194.90	$194.90
7 purchase totals =	$967.41		$1,056.3583	$1,056.35	$1,056.30	$1,056.40