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	$190.83	13.337%	$216.281	$216.28	$216.30	$216.30
Purchase #2	$242.53	5.505%	$255.8813	$255.88	$255.90	$255.90
Purchase #3	$239.47	6.105%	$254.0896	$254.09	$254.10	$254.10
Purchase #4	$98.47	5.606%	$103.9902	$103.99	$104.00	$104.00
Purchase #5	$40.71	12.484%	$45.7922	$45.79	$45.80	$45.80
Purchase #6	$19.43	3.673%	$20.1437	$20.14	$20.15	$20.10
Purchase #7	$111.89	9.831%	$122.8899	$122.89	$122.90	$122.90
7 purchase totals =	$943.33		$1,019.0679	$1,019.06	$1,019.15	$1,019.10