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	$183.42	12.732%	$206.773	$206.77	$206.75	$206.80
Purchase #2	$250.58	11.307%	$278.9131	$278.91	$278.90	$278.90
Purchase #3	$137.77	11.300%	$153.338	$153.34	$153.35	$153.30
Purchase #4	$95.45	5.650%	$100.8429	$100.84	$100.85	$100.80
Purchase #5	$173.46	6.420%	$184.5961	$184.60	$184.60	$184.60
Purchase #6	$42.94	8.102%	$46.419	$46.42	$46.40	$46.40
Purchase #7	$48.66	12.413%	$54.7002	$54.70	$54.70	$54.70
7 purchase totals =	$932.28		$1,025.5823	$1,025.58	$1,025.55	$1,025.50