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	$72.27	7.407%	$77.623	$77.62	$77.60	$77.60
Purchase #2	$170.39	9.352%	$186.3249	$186.32	$186.30	$186.30
Purchase #3	$203.81	3.273%	$210.4807	$210.48	$210.50	$210.50
Purchase #4	$63.28	10.651%	$70.02	$70.02	$70.00	$70.00
Purchase #5	$224.45	7.698%	$241.7282	$241.73	$241.75	$241.70
Purchase #6	$230.59	10.594%	$255.0187	$255.02	$255.00	$255.00
Purchase #7	$158.82	9.450%	$173.8285	$173.83	$173.85	$173.80
7 purchase totals =	$1,123.61		$1,215.0240	$1,215.02	$1,215.00	$1,214.90