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	$197.32	10.169%	$217.3855	$217.39	$217.40	$217.40
Purchase #2	$136.90	12.148%	$153.5306	$153.53	$153.55	$153.50
Purchase #3	$135.77	13.481%	$154.0732	$154.07	$154.05	$154.10
Purchase #4	$200.68	11.678%	$224.1154	$224.12	$224.10	$224.10
Purchase #5	$96.45	9.661%	$105.768	$105.77	$105.75	$105.80
Purchase #6	$98.60	5.356%	$103.881	$103.88	$103.90	$103.90
Purchase #7	$37.29	11.523%	$41.5869	$41.59	$41.60	$41.60
7 purchase totals =	$903.01		$1,000.3406	$1,000.35	$1,000.35	$1,000.40