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	$177.68	10.826%	$196.9156	$196.92	$196.90	$196.90
Purchase #2	$15.39	6.482%	$16.3876	$16.39	$16.40	$16.40
Purchase #3	$61.49	8.315%	$66.6029	$66.60	$66.60	$66.60
Purchase #4	$127.81	13.556%	$145.1359	$145.14	$145.15	$145.10
Purchase #5	$6.72	7.745%	$7.2405	$7.24	$7.25	$7.20
Purchase #6	$99.47	4.353%	$103.7999	$103.80	$103.80	$103.80
Purchase #7	$168.80	10.548%	$186.605	$186.61	$186.60	$186.60
7 purchase totals =	$657.36		$722.6874	$722.70	$722.70	$722.60