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	$48.97	9.430%	$53.5879	$53.59	$53.60	$53.60
Purchase #2	$49.56	10.678%	$54.852	$54.85	$54.85	$54.90
Purchase #3	$168.77	11.680%	$188.4823	$188.48	$188.50	$188.50
Purchase #4	$174.56	6.129%	$185.2588	$185.26	$185.25	$185.30
Purchase #5	$106.61	13.513%	$121.0162	$121.02	$121.00	$121.00
Purchase #6	$236.67	10.435%	$261.3665	$261.37	$261.35	$261.40
Purchase #7	$70.25	8.247%	$76.0435	$76.04	$76.05	$76.00
7 purchase totals =	$855.39		$940.6072	$940.61	$940.60	$940.70