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	$105.94	5.421%	$111.683	$111.68	$111.70	$111.70
Purchase #2	$218.77	8.439%	$237.232	$237.23	$237.25	$237.20
Purchase #3	$142.83	13.704%	$162.4034	$162.40	$162.40	$162.40
Purchase #4	$168.78	5.689%	$178.3819	$178.38	$178.40	$178.40
Purchase #5	$31.80	12.722%	$35.8456	$35.85	$35.85	$35.80
Purchase #6	$244.53	8.704%	$265.8139	$265.81	$265.80	$265.80
Purchase #7	$96.51	8.780%	$104.9836	$104.98	$105.00	$105.00
7 purchase totals =	$1,009.16		$1,096.3434	$1,096.33	$1,096.40	$1,096.30