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	$20.69	8.823%	$22.5155	$22.52	$22.50	$22.50
Purchase #2	$42.56	5.863%	$45.0553	$45.06	$45.05	$45.10
Purchase #3	$44.95	11.629%	$50.1772	$50.18	$50.20	$50.20
Purchase #4	$88.61	13.636%	$100.6929	$100.69	$100.70	$100.70
Purchase #5	$142.95	9.212%	$156.1186	$156.12	$156.10	$156.10
Purchase #6	$226.61	6.641%	$241.6592	$241.66	$241.65	$241.70
Purchase #7	$149.38	4.658%	$156.3381	$156.34	$156.35	$156.30
7 purchase totals =	$715.75		$772.5568	$772.57	$772.55	$772.60