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	$190.98	9.171%	$208.4948	$208.49	$208.50	$208.50
Purchase #2	$117.27	5.387%	$123.5873	$123.59	$123.60	$123.60
Purchase #3	$116.64	10.852%	$129.2978	$129.30	$129.30	$129.30
Purchase #4	$13.32	13.116%	$15.0671	$15.07	$15.05	$15.10
Purchase #5	$29.61	6.415%	$31.5095	$31.51	$31.50	$31.50
Purchase #6	$98.77	10.113%	$108.7586	$108.76	$108.75	$108.80
Purchase #7	$234.38	10.723%	$259.5126	$259.51	$259.50	$259.50
7 purchase totals =	$800.97		$876.2277	$876.23	$876.20	$876.30