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	$196.86	10.697%	$217.9181	$217.92	$217.90	$217.90
Purchase #2	$58.65	6.795%	$62.6353	$62.64	$62.65	$62.60
Purchase #3	$28.85	13.646%	$32.7869	$32.79	$32.80	$32.80
Purchase #4	$73.31	3.144%	$75.6149	$75.61	$75.60	$75.60
Purchase #5	$50.29	3.730%	$52.1658	$52.17	$52.15	$52.20
Purchase #6	$52.59	4.390%	$54.8987	$54.90	$54.90	$54.90
Purchase #7	$103.80	13.452%	$117.7632	$117.76	$117.75	$117.80
7 purchase totals =	$564.35		$613.7829	$613.79	$613.75	$613.80