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	$168.89	12.306%	$189.6736	$189.67	$189.65	$189.70
Purchase #2	$73.77	3.801%	$76.574	$76.57	$76.55	$76.60
Purchase #3	$50.76	6.721%	$54.1716	$54.17	$54.15	$54.20
Purchase #4	$235.75	10.613%	$260.7701	$260.77	$260.75	$260.80
Purchase #5	$99.66	3.502%	$103.1501	$103.15	$103.15	$103.20
Purchase #6	$244.72	4.374%	$255.4241	$255.42	$255.40	$255.40
Purchase #7	$20.45	10.548%	$22.6071	$22.61	$22.60	$22.60
7 purchase totals =	$894.00		$962.3706	$962.36	$962.25	$962.50