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	$169.71	6.615%	$180.9363	$180.94	$180.95	$180.90
Purchase #2	$224.63	10.669%	$248.5958	$248.60	$248.60	$248.60
Purchase #3	$37.27	8.233%	$40.3384	$40.34	$40.35	$40.30
Purchase #4	$77.76	12.427%	$87.4232	$87.42	$87.40	$87.40
Purchase #5	$212.59	12.158%	$238.4367	$238.44	$238.45	$238.40
Purchase #6	$61.70	9.182%	$67.3653	$67.37	$67.35	$67.40
Purchase #7	$159.98	7.660%	$172.2345	$172.23	$172.25	$172.20
7 purchase totals =	$943.64		$1,035.3302	$1,035.34	$1,035.35	$1,035.20