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	$132.41	9.676%	$145.222	$145.22	$145.20	$145.20
Purchase #2	$182.42	4.625%	$190.8569	$190.86	$190.85	$190.90
Purchase #3	$87.27	6.153%	$92.6397	$92.64	$92.65	$92.60
Purchase #4	$198.92	9.741%	$218.2968	$218.30	$218.30	$218.30
Purchase #5	$42.27	8.773%	$45.9783	$45.98	$46.00	$46.00
Purchase #6	$141.73	7.285%	$152.055	$152.06	$152.05	$152.10
Purchase #7	$52.98	6.392%	$56.3665	$56.37	$56.35	$56.40
7 purchase totals =	$838.00		$901.4152	$901.43	$901.40	$901.50