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	$96.59	9.667%	$105.9274	$105.93	$105.95	$105.90
Purchase #2	$132.32	13.575%	$150.2824	$150.28	$150.30	$150.30
Purchase #3	$163.70	9.856%	$179.8343	$179.83	$179.85	$179.80
Purchase #4	$106.29	6.846%	$113.5666	$113.57	$113.55	$113.60
Purchase #5	$67.80	11.541%	$75.6248	$75.62	$75.60	$75.60
Purchase #6	$104.25	11.244%	$115.9719	$115.97	$115.95	$116.00
Purchase #7	$65.30	11.317%	$72.69	$72.69	$72.70	$72.70
7 purchase totals =	$736.25		$813.8974	$813.89	$813.90	$813.90