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	$153.25	8.457%	$166.2104	$166.21	$166.20	$166.20
Purchase #2	$160.30	5.221%	$168.6693	$168.67	$168.65	$168.70
Purchase #3	$95.96	4.380%	$100.163	$100.16	$100.15	$100.20
Purchase #4	$158.61	13.249%	$179.6242	$179.62	$179.60	$179.60
Purchase #5	$40.69	8.292%	$44.064	$44.06	$44.05	$44.10
Purchase #6	$51.76	11.434%	$57.6782	$57.68	$57.70	$57.70
Purchase #7	$127.81	12.301%	$143.5319	$143.53	$143.55	$143.50
7 purchase totals =	$788.38		$859.9410	$859.93	$859.90	$860.00