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	$181.78	4.431%	$189.8347	$189.83	$189.85	$189.80
Purchase #2	$75.94	7.763%	$81.8352	$81.84	$81.85	$81.80
Purchase #3	$137.79	5.322%	$145.1232	$145.12	$145.10	$145.10
Purchase #4	$40.84	11.199%	$45.4137	$45.41	$45.40	$45.40
Purchase #5	$186.78	13.252%	$211.5321	$211.53	$211.55	$211.50
Purchase #6	$141.75	8.563%	$153.8881	$153.89	$153.90	$153.90
Purchase #7	$95.83	10.122%	$105.5299	$105.53	$105.55	$105.50
7 purchase totals =	$860.71		$933.1569	$933.15	$933.20	$933.00