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	$82.71	3.667%	$85.743	$85.74	$85.75	$85.70
Purchase #2	$212.48	4.250%	$221.5104	$221.51	$221.50	$221.50
Purchase #3	$93.45	10.835%	$103.5753	$103.58	$103.60	$103.60
Purchase #4	$18.95	11.282%	$21.0879	$21.09	$21.10	$21.10
Purchase #5	$51.28	10.223%	$56.5224	$56.52	$56.50	$56.50
Purchase #6	$19.79	7.196%	$21.2141	$21.21	$21.20	$21.20
Purchase #7	$54.52	11.817%	$60.9626	$60.96	$60.95	$61.00
7 purchase totals =	$533.18		$570.6157	$570.61	$570.60	$570.60