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	$194.41	12.569%	$218.8454	$218.85	$218.85	$218.80
Purchase #2	$55.38	11.240%	$61.6047	$61.60	$61.60	$61.60
Purchase #3	$82.73	5.675%	$87.4249	$87.42	$87.40	$87.40
Purchase #4	$154.94	12.251%	$173.9217	$173.92	$173.90	$173.90
Purchase #5	$175.49	11.862%	$196.3066	$196.31	$196.30	$196.30
Purchase #6	$72.94	11.687%	$81.4645	$81.46	$81.45	$81.50
Purchase #7	$158.70	3.493%	$164.2434	$164.24	$164.25	$164.20
7 purchase totals =	$894.59		$983.8112	$983.80	$983.75	$983.70