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	$92.82	7.318%	$99.6126	$99.61	$99.60	$99.60
Purchase #2	$169.70	13.567%	$192.7232	$192.72	$192.70	$192.70
Purchase #3	$151.67	10.751%	$167.976	$167.98	$168.00	$168.00
Purchase #4	$77.78	4.229%	$81.0693	$81.07	$81.05	$81.10
Purchase #5	$172.77	11.385%	$192.4399	$192.44	$192.45	$192.40
Purchase #6	$93.82	6.195%	$99.6321	$99.63	$99.65	$99.60
Purchase #7	$82.32	7.845%	$88.778	$88.78	$88.80	$88.80
7 purchase totals =	$840.88		$922.2311	$922.23	$922.25	$922.20