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	$78.65	11.273%	$87.5162	$87.52	$87.50	$87.50
Purchase #2	$150.57	5.219%	$158.4282	$158.43	$158.45	$158.40
Purchase #3	$198.84	7.240%	$213.236	$213.24	$213.25	$213.20
Purchase #4	$145.35	5.874%	$153.8879	$153.89	$153.90	$153.90
Purchase #5	$48.95	6.684%	$52.2218	$52.22	$52.20	$52.20
Purchase #6	$173.96	9.410%	$190.3296	$190.33	$190.35	$190.30
Purchase #7	$236.99	7.202%	$254.058	$254.06	$254.05	$254.10
7 purchase totals =	$1,033.31		$1,109.6777	$1,109.69	$1,109.70	$1,109.60