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	$144.27	4.329%	$150.5154	$150.52	$150.50	$150.50
Purchase #2	$222.83	3.764%	$231.2173	$231.22	$231.20	$231.20
Purchase #3	$155.82	5.710%	$164.7173	$164.72	$164.70	$164.70
Purchase #4	$169.31	8.873%	$184.3329	$184.33	$184.35	$184.30
Purchase #5	$197.50	9.600%	$216.46	$216.46	$216.45	$216.50
Purchase #6	$215.90	6.656%	$230.2703	$230.27	$230.25	$230.30
Purchase #7	$130.52	11.849%	$145.9853	$145.99	$146.00	$146.00
7 purchase totals =	$1,236.15		$1,323.4985	$1,323.51	$1,323.45	$1,323.50