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	$216.45	4.827%	$226.898	$226.90	$226.90	$226.90
Purchase #2	$137.80	4.503%	$144.0051	$144.01	$144.00	$144.00
Purchase #3	$92.42	13.259%	$104.674	$104.67	$104.65	$104.70
Purchase #4	$85.46	5.843%	$90.4534	$90.45	$90.45	$90.50
Purchase #5	$128.86	12.570%	$145.0577	$145.06	$145.05	$145.10
Purchase #6	$159.35	10.390%	$175.9065	$175.91	$175.90	$175.90
Purchase #7	$59.98	7.726%	$64.6141	$64.61	$64.60	$64.60
7 purchase totals =	$880.32		$951.6088	$951.61	$951.55	$951.70