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	$38.88	11.103%	$43.1968	$43.20	$43.20	$43.20
Purchase #2	$103.92	5.306%	$109.434	$109.43	$109.45	$109.40
Purchase #3	$173.35	6.626%	$184.8362	$184.84	$184.85	$184.80
Purchase #4	$236.60	9.861%	$259.9311	$259.93	$259.95	$259.90
Purchase #5	$74.32	5.578%	$78.4656	$78.47	$78.45	$78.50
Purchase #6	$73.72	6.325%	$78.3828	$78.38	$78.40	$78.40
Purchase #7	$117.99	11.615%	$131.6945	$131.69	$131.70	$131.70
7 purchase totals =	$818.78		$885.9410	$885.94	$886.00	$885.90