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	$47.86	3.679%	$49.6208	$49.62	$49.60	$49.60
Purchase #2	$210.72	5.576%	$222.4697	$222.47	$222.45	$222.50
Purchase #3	$185.28	8.312%	$200.6805	$200.68	$200.70	$200.70
Purchase #4	$97.85	12.128%	$109.7172	$109.72	$109.70	$109.70
Purchase #5	$41.75	5.773%	$44.1602	$44.16	$44.15	$44.20
Purchase #6	$241.85	3.386%	$250.039	$250.04	$250.05	$250.00
Purchase #7	$240.90	12.691%	$271.4726	$271.47	$271.45	$271.50
7 purchase totals =	$1,066.21		$1,148.1600	$1,148.16	$1,148.10	$1,148.20