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	$63.93	13.553%	$72.5944	$72.59	$72.60	$72.60
Purchase #2	$21.55	4.402%	$22.4986	$22.50	$22.50	$22.50
Purchase #3	$176.89	9.776%	$194.1828	$194.18	$194.20	$194.20
Purchase #4	$38.60	10.166%	$42.5241	$42.52	$42.50	$42.50
Purchase #5	$9.26	9.711%	$10.1592	$10.16	$10.15	$10.20
Purchase #6	$50.56	10.699%	$55.9694	$55.97	$55.95	$56.00
Purchase #7	$164.37	4.538%	$171.8291	$171.83	$171.85	$171.80
7 purchase totals =	$525.16		$569.7576	$569.75	$569.75	$569.80