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	$151.72	11.285%	$168.8416	$168.84	$168.85	$168.80
Purchase #2	$148.60	13.150%	$168.1409	$168.14	$168.15	$168.10
Purchase #3	$184.59	11.455%	$205.7348	$205.73	$205.75	$205.70
Purchase #4	$80.80	11.824%	$90.3538	$90.35	$90.35	$90.40
Purchase #5	$53.60	13.503%	$60.8376	$60.84	$60.85	$60.80
Purchase #6	$192.73	10.268%	$212.5195	$212.52	$212.50	$212.50
Purchase #7	$239.82	5.833%	$253.8087	$253.81	$253.80	$253.80
7 purchase totals =	$1,051.86		$1,160.2369	$1,160.23	$1,160.25	$1,160.10