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	$126.36	5.611%	$133.4501	$133.45	$133.45	$133.50
Purchase #2	$229.50	11.488%	$255.865	$255.87	$255.85	$255.90
Purchase #3	$130.54	4.197%	$136.0188	$136.02	$136.00	$136.00
Purchase #4	$42.58	7.554%	$45.7965	$45.80	$45.80	$45.80
Purchase #5	$79.28	9.191%	$86.5666	$86.57	$86.55	$86.60
Purchase #6	$81.83	10.584%	$90.4909	$90.49	$90.50	$90.50
Purchase #7	$135.32	13.248%	$153.2472	$153.25	$153.25	$153.20
7 purchase totals =	$825.41		$901.4351	$901.45	$901.40	$901.50