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	$224.61	13.541%	$255.0244	$255.02	$255.00	$255.00
Purchase #2	$78.38	5.148%	$82.415	$82.42	$82.40	$82.40
Purchase #3	$107.79	3.669%	$111.7448	$111.74	$111.75	$111.70
Purchase #4	$142.38	8.126%	$153.9498	$153.95	$153.95	$153.90
Purchase #5	$87.33	5.237%	$91.9035	$91.90	$91.90	$91.90
Purchase #6	$24.86	11.116%	$27.6234	$27.62	$27.60	$27.60
Purchase #7	$201.79	13.868%	$229.7742	$229.77	$229.75	$229.80
7 purchase totals =	$867.14		$952.4351	$952.42	$952.35	$952.30