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	$9.44	3.189%	$9.741	$9.74	$9.75	$9.70
Purchase #2	$52.38	13.439%	$59.4193	$59.42	$59.40	$59.40
Purchase #3	$153.60	3.390%	$158.807	$158.81	$158.80	$158.80
Purchase #4	$172.58	11.759%	$192.8737	$192.87	$192.85	$192.90
Purchase #5	$82.54	4.658%	$86.3847	$86.38	$86.40	$86.40
Purchase #6	$195.36	6.738%	$208.5234	$208.52	$208.50	$208.50
Purchase #7	$103.68	7.801%	$111.7681	$111.77	$111.75	$111.80
7 purchase totals =	$769.58		$827.5172	$827.51	$827.45	$827.50