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	$177.85	5.696%	$187.9803	$187.98	$188.00	$188.00
Purchase #2	$247.94	6.256%	$263.4511	$263.45	$263.45	$263.50
Purchase #3	$45.82	10.439%	$50.6031	$50.60	$50.60	$50.60
Purchase #4	$134.55	12.855%	$151.8464	$151.85	$151.85	$151.80
Purchase #5	$152.47	9.849%	$167.4868	$167.49	$167.50	$167.50
Purchase #6	$112.28	5.239%	$118.1623	$118.16	$118.15	$118.20
Purchase #7	$149.64	4.696%	$156.6671	$156.67	$156.65	$156.70
7 purchase totals =	$1,020.55		$1,096.1971	$1,096.20	$1,096.20	$1,096.30