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	$145.82	11.536%	$162.6418	$162.64	$162.65	$162.60
Purchase #2	$12.45	10.844%	$13.8001	$13.80	$13.80	$13.80
Purchase #3	$128.50	8.439%	$139.3441	$139.34	$139.35	$139.30
Purchase #4	$82.97	4.282%	$86.5228	$86.52	$86.50	$86.50
Purchase #5	$36.35	3.496%	$37.6208	$37.62	$37.60	$37.60
Purchase #6	$186.59	13.358%	$211.5147	$211.51	$211.50	$211.50
Purchase #7	$116.81	8.616%	$126.8743	$126.87	$126.85	$126.90
7 purchase totals =	$709.49		$778.3186	$778.30	$778.25	$778.20