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	$153.95	9.729%	$168.9278	$168.93	$168.95	$168.90
Purchase #2	$73.78	3.682%	$76.4966	$76.50	$76.50	$76.50
Purchase #3	$152.99	9.687%	$167.8101	$167.81	$167.80	$167.80
Purchase #4	$166.61	5.436%	$175.6669	$175.67	$175.65	$175.70
Purchase #5	$104.76	6.113%	$111.164	$111.16	$111.15	$111.20
Purchase #6	$148.73	6.644%	$158.6116	$158.61	$158.60	$158.60
Purchase #7	$42.65	3.748%	$44.2485	$44.25	$44.25	$44.20
7 purchase totals =	$843.47		$902.9255	$902.93	$902.90	$902.90