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	$9.66	12.447%	$10.8624	$10.86	$10.85	$10.90
Purchase #2	$85.70	7.543%	$92.1644	$92.16	$92.15	$92.20
Purchase #3	$147.95	11.187%	$164.5012	$164.50	$164.50	$164.50
Purchase #4	$144.45	13.640%	$164.153	$164.15	$164.15	$164.20
Purchase #5	$190.43	8.371%	$206.3709	$206.37	$206.35	$206.40
Purchase #6	$186.58	13.107%	$211.035	$211.04	$211.05	$211.00
Purchase #7	$151.80	9.642%	$166.4366	$166.44	$166.45	$166.40
7 purchase totals =	$916.57		$1,015.5235	$1,015.52	$1,015.50	$1,015.60