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	$182.29	9.396%	$199.418	$199.42	$199.40	$199.40
Purchase #2	$205.66	10.596%	$227.4517	$227.45	$227.45	$227.50
Purchase #3	$236.44	12.422%	$265.8106	$265.81	$265.80	$265.80
Purchase #4	$46.42	6.492%	$49.4336	$49.43	$49.45	$49.40
Purchase #5	$109.42	9.578%	$119.9002	$119.90	$119.90	$119.90
Purchase #6	$160.69	5.321%	$169.2403	$169.24	$169.25	$169.20
Purchase #7	$100.68	11.111%	$111.8666	$111.87	$111.85	$111.90
7 purchase totals =	$1,041.60		$1,143.1210	$1,143.12	$1,143.10	$1,143.10