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	$132.70	12.157%	$148.8323	$148.83	$148.85	$148.80
Purchase #2	$230.54	5.130%	$242.3667	$242.37	$242.35	$242.40
Purchase #3	$85.71	4.762%	$89.7915	$89.79	$89.80	$89.80
Purchase #4	$238.28	10.193%	$262.5679	$262.57	$262.55	$262.60
Purchase #5	$197.34	3.688%	$204.6179	$204.62	$204.60	$204.60
Purchase #6	$212.98	6.753%	$227.3625	$227.36	$227.35	$227.40
Purchase #7	$23.46	4.570%	$24.5321	$24.53	$24.55	$24.50
7 purchase totals =	$1,121.01		$1,200.0709	$1,200.07	$1,200.05	$1,200.10