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	$173.41	13.297%	$196.4683	$196.47	$196.45	$196.50
Purchase #2	$18.45	7.109%	$19.7616	$19.76	$19.75	$19.80
Purchase #3	$243.61	12.864%	$274.948	$274.95	$274.95	$274.90
Purchase #4	$46.53	4.595%	$48.6681	$48.67	$48.65	$48.70
Purchase #5	$183.42	4.625%	$191.9032	$191.90	$191.90	$191.90
Purchase #6	$95.92	8.538%	$104.1096	$104.11	$104.10	$104.10
Purchase #7	$138.45	10.793%	$153.3929	$153.39	$153.40	$153.40
7 purchase totals =	$899.79		$989.2517	$989.25	$989.20	$989.30