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	$228.96	9.549%	$250.8234	$250.82	$250.80	$250.80
Purchase #2	$47.99	13.748%	$54.5877	$54.59	$54.60	$54.60
Purchase #3	$9.96	8.421%	$10.7987	$10.80	$10.80	$10.80
Purchase #4	$214.46	12.583%	$241.4455	$241.45	$241.45	$241.40
Purchase #5	$179.71	3.248%	$185.547	$185.55	$185.55	$185.50
Purchase #6	$37.35	11.629%	$41.6934	$41.69	$41.70	$41.70
Purchase #7	$246.32	6.488%	$262.3012	$262.30	$262.30	$262.30
7 purchase totals =	$964.75		$1,047.1969	$1,047.20	$1,047.20	$1,047.10