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	$168.34	10.224%	$185.5511	$185.55	$185.55	$185.60
Purchase #2	$219.67	11.208%	$244.2906	$244.29	$244.30	$244.30
Purchase #3	$129.47	6.215%	$137.5166	$137.52	$137.50	$137.50
Purchase #4	$134.40	4.513%	$140.4655	$140.47	$140.45	$140.50
Purchase #5	$60.88	13.798%	$69.2802	$69.28	$69.30	$69.30
Purchase #6	$164.52	5.607%	$173.7446	$173.74	$173.75	$173.70
Purchase #7	$189.87	5.209%	$199.7603	$199.76	$199.75	$199.80
7 purchase totals =	$1,067.15		$1,150.6089	$1,150.61	$1,150.60	$1,150.70