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	$70.54	11.546%	$78.6845	$78.68	$78.70	$78.70
Purchase #2	$67.39	11.271%	$74.9855	$74.99	$75.00	$75.00
Purchase #3	$130.69	13.292%	$148.0613	$148.06	$148.05	$148.10
Purchase #4	$43.52	13.727%	$49.494	$49.49	$49.50	$49.50
Purchase #5	$138.31	9.586%	$151.5684	$151.57	$151.55	$151.60
Purchase #6	$31.58	3.195%	$32.589	$32.59	$32.60	$32.60
Purchase #7	$30.52	6.480%	$32.4977	$32.50	$32.50	$32.50
7 purchase totals =	$512.55		$567.8804	$567.88	$567.90	$568.00