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	$247.52	10.627%	$273.824	$273.82	$273.80	$273.80
Purchase #2	$190.87	7.772%	$205.7044	$205.70	$205.70	$205.70
Purchase #3	$175.84	9.752%	$192.9879	$192.99	$193.00	$193.00
Purchase #4	$75.32	9.664%	$82.5989	$82.60	$82.60	$82.60
Purchase #5	$231.58	3.861%	$240.5213	$240.52	$240.50	$240.50
Purchase #6	$80.40	11.372%	$89.5431	$89.54	$89.55	$89.50
Purchase #7	$194.52	4.503%	$203.2792	$203.28	$203.30	$203.30
7 purchase totals =	$1,196.05		$1,288.4588	$1,288.45	$1,288.45	$1,288.40