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	$139.75	4.196%	$145.6139	$145.61	$145.60	$145.60
Purchase #2	$137.98	8.614%	$149.8656	$149.87	$149.85	$149.90
Purchase #3	$169.70	11.209%	$188.7217	$188.72	$188.70	$188.70
Purchase #4	$219.90	7.848%	$237.1578	$237.16	$237.15	$237.20
Purchase #5	$113.79	5.186%	$119.6911	$119.69	$119.70	$119.70
Purchase #6	$152.62	13.194%	$172.7567	$172.76	$172.75	$172.80
Purchase #7	$125.38	4.540%	$131.0723	$131.07	$131.05	$131.10
7 purchase totals =	$1,059.12		$1,144.8791	$1,144.88	$1,144.80	$1,145.00