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	$86.69	8.289%	$93.8757	$93.88	$93.90	$93.90
Purchase #2	$64.86	13.446%	$73.5811	$73.58	$73.60	$73.60
Purchase #3	$248.79	6.458%	$264.8569	$264.86	$264.85	$264.90
Purchase #4	$118.25	10.177%	$130.2843	$130.28	$130.30	$130.30
Purchase #5	$76.59	13.359%	$86.8217	$86.82	$86.80	$86.80
Purchase #6	$74.90	5.300%	$78.8697	$78.87	$78.85	$78.90
Purchase #7	$60.75	9.246%	$66.3669	$66.37	$66.35	$66.40
7 purchase totals =	$730.83		$794.6563	$794.66	$794.65	$794.80