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	$127.61	5.726%	$134.9169	$134.92	$134.90	$134.90
Purchase #2	$145.46	13.131%	$164.5604	$164.56	$164.55	$164.60
Purchase #3	$222.33	8.633%	$241.5237	$241.52	$241.50	$241.50
Purchase #4	$176.64	9.517%	$193.4508	$193.45	$193.45	$193.50
Purchase #5	$99.34	3.651%	$102.9669	$102.97	$102.95	$103.00
Purchase #6	$83.53	12.428%	$93.9111	$93.91	$93.90	$93.90
Purchase #7	$149.28	4.230%	$155.5945	$155.59	$155.60	$155.60
7 purchase totals =	$1,004.19		$1,086.9243	$1,086.92	$1,086.85	$1,087.00