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	$153.29	6.289%	$162.9304	$162.93	$162.95	$162.90
Purchase #2	$208.45	8.679%	$226.5414	$226.54	$226.55	$226.50
Purchase #3	$65.60	12.757%	$73.9686	$73.97	$73.95	$74.00
Purchase #4	$129.90	11.536%	$144.8853	$144.89	$144.90	$144.90
Purchase #5	$48.33	4.331%	$50.4232	$50.42	$50.40	$50.40
Purchase #6	$212.43	13.644%	$241.4139	$241.41	$241.40	$241.40
Purchase #7	$107.89	10.699%	$119.4332	$119.43	$119.45	$119.40
7 purchase totals =	$925.89		$1,019.5960	$1,019.59	$1,019.60	$1,019.50