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	$123.25	10.641%	$136.365	$136.37	$136.35	$136.40
Purchase #2	$33.65	11.347%	$37.4683	$37.47	$37.45	$37.50
Purchase #3	$171.43	10.567%	$189.545	$189.55	$189.55	$189.50
Purchase #4	$39.94	13.753%	$45.4329	$45.43	$45.45	$45.40
Purchase #5	$236.55	12.571%	$266.2867	$266.29	$266.30	$266.30
Purchase #6	$21.72	3.669%	$22.5169	$22.52	$22.50	$22.50
Purchase #7	$123.69	8.714%	$134.4683	$134.47	$134.45	$134.50
7 purchase totals =	$750.23		$832.0831	$832.10	$832.05	$832.10