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	$212.28	12.329%	$238.452	$238.45	$238.45	$238.50
Purchase #2	$47.28	12.298%	$53.0945	$53.09	$53.10	$53.10
Purchase #3	$210.32	3.680%	$218.0598	$218.06	$218.05	$218.10
Purchase #4	$159.55	8.680%	$173.3989	$173.40	$173.40	$173.40
Purchase #5	$59.74	13.110%	$67.5719	$67.57	$67.55	$67.60
Purchase #6	$32.56	4.258%	$33.9464	$33.95	$33.95	$33.90
Purchase #7	$214.29	13.309%	$242.8099	$242.81	$242.80	$242.80
7 purchase totals =	$936.02		$1,027.3334	$1,027.33	$1,027.30	$1,027.40