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	$148.58	13.476%	$168.6026	$168.60	$168.60	$168.60
Purchase #2	$138.42	10.239%	$152.5928	$152.59	$152.60	$152.60
Purchase #3	$122.45	6.559%	$130.4815	$130.48	$130.50	$130.50
Purchase #4	$212.61	3.167%	$219.3434	$219.34	$219.35	$219.30
Purchase #5	$196.65	9.254%	$214.848	$214.85	$214.85	$214.80
Purchase #6	$20.38	12.292%	$22.8851	$22.89	$22.90	$22.90
Purchase #7	$57.57	5.662%	$60.8296	$60.83	$60.85	$60.80
7 purchase totals =	$896.66		$969.5830	$969.58	$969.65	$969.50