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	$153.84	3.628%	$159.4213	$159.42	$159.40	$159.40
Purchase #2	$185.94	5.537%	$196.2355	$196.24	$196.25	$196.20
Purchase #3	$54.72	7.627%	$58.8935	$58.89	$58.90	$58.90
Purchase #4	$80.50	8.515%	$87.3546	$87.35	$87.35	$87.40
Purchase #5	$101.60	10.643%	$112.4133	$112.41	$112.40	$112.40
Purchase #6	$64.49	10.826%	$71.4717	$71.47	$71.45	$71.50
Purchase #7	$102.70	12.212%	$115.2417	$115.24	$115.25	$115.20
7 purchase totals =	$743.79		$801.0316	$801.02	$801.00	$801.00