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	$167.42	4.692%	$175.2753	$175.28	$175.30	$175.30
Purchase #2	$60.87	7.572%	$65.4791	$65.48	$65.50	$65.50
Purchase #3	$66.93	6.864%	$71.5241	$71.52	$71.50	$71.50
Purchase #4	$154.88	6.169%	$164.4345	$164.43	$164.45	$164.40
Purchase #5	$234.94	7.373%	$252.2621	$252.26	$252.25	$252.30
Purchase #6	$82.55	10.188%	$90.9602	$90.96	$90.95	$91.00
Purchase #7	$7.45	13.593%	$8.4627	$8.46	$8.45	$8.50
7 purchase totals =	$775.04		$828.3980	$828.39	$828.40	$828.50