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	$76.70	13.392%	$86.9717	$86.97	$86.95	$87.00
Purchase #2	$244.81	4.762%	$256.4679	$256.47	$256.45	$256.50
Purchase #3	$72.30	5.653%	$76.3871	$76.39	$76.40	$76.40
Purchase #4	$37.85	13.241%	$42.8617	$42.86	$42.85	$42.90
Purchase #5	$142.48	5.687%	$150.5828	$150.58	$150.60	$150.60
Purchase #6	$118.55	11.388%	$132.0505	$132.05	$132.05	$132.10
Purchase #7	$150.91	10.474%	$166.7163	$166.72	$166.70	$166.70
7 purchase totals =	$843.60		$912.0380	$912.04	$912.00	$912.20