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	$83.55	9.526%	$91.509	$91.51	$91.50	$91.50
Purchase #2	$198.36	12.852%	$223.8532	$223.85	$223.85	$223.90
Purchase #3	$76.86	3.753%	$79.7446	$79.74	$79.75	$79.70
Purchase #4	$228.34	7.187%	$244.7508	$244.75	$244.75	$244.80
Purchase #5	$235.95	11.794%	$263.7779	$263.78	$263.80	$263.80
Purchase #6	$175.45	8.537%	$190.4282	$190.43	$190.45	$190.40
Purchase #7	$100.86	5.616%	$106.5243	$106.52	$106.50	$106.50
7 purchase totals =	$1,099.37		$1,200.5880	$1,200.58	$1,200.60	$1,200.60