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	$216.39	6.211%	$229.83	$229.83	$229.85	$229.80
Purchase #2	$11.93	3.756%	$12.3781	$12.38	$12.40	$12.40
Purchase #3	$61.70	13.141%	$69.808	$69.81	$69.80	$69.80
Purchase #4	$85.87	5.723%	$90.7843	$90.78	$90.80	$90.80
Purchase #5	$146.50	12.470%	$164.7686	$164.77	$164.75	$164.80
Purchase #6	$32.43	3.563%	$33.5855	$33.59	$33.60	$33.60
Purchase #7	$23.44	6.743%	$25.0206	$25.02	$25.00	$25.00
7 purchase totals =	$578.26		$626.1751	$626.18	$626.20	$626.20