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	$106.71	5.458%	$112.5342	$112.53	$112.55	$112.50
Purchase #2	$234.38	5.848%	$248.0865	$248.09	$248.10	$248.10
Purchase #3	$95.34	5.152%	$100.2519	$100.25	$100.25	$100.30
Purchase #4	$211.40	4.189%	$220.2555	$220.26	$220.25	$220.30
Purchase #5	$151.84	13.435%	$172.2397	$172.24	$172.25	$172.20
Purchase #6	$140.82	12.617%	$158.5873	$158.59	$158.60	$158.60
Purchase #7	$190.84	10.759%	$211.3725	$211.37	$211.35	$211.40
7 purchase totals =	$1,131.33		$1,223.3276	$1,223.33	$1,223.35	$1,223.40