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	$159.88	8.624%	$173.6681	$173.67	$173.65	$173.70
Purchase #2	$41.90	9.406%	$45.8411	$45.84	$45.85	$45.80
Purchase #3	$53.72	5.115%	$56.4678	$56.47	$56.45	$56.50
Purchase #4	$38.36	13.598%	$43.5762	$43.58	$43.60	$43.60
Purchase #5	$154.56	11.592%	$172.4766	$172.48	$172.50	$172.50
Purchase #6	$245.34	11.370%	$273.2352	$273.24	$273.25	$273.20
Purchase #7	$158.49	12.329%	$178.0302	$178.03	$178.05	$178.00
7 purchase totals =	$852.25		$943.2952	$943.31	$943.35	$943.30