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	$223.64	3.259%	$230.9284	$230.93	$230.95	$230.90
Purchase #2	$149.74	10.871%	$166.0182	$166.02	$166.00	$166.00
Purchase #3	$90.72	13.863%	$103.2965	$103.30	$103.30	$103.30
Purchase #4	$143.65	13.671%	$163.2884	$163.29	$163.30	$163.30
Purchase #5	$241.77	13.397%	$274.1599	$274.16	$274.15	$274.20
Purchase #6	$208.89	13.714%	$237.5372	$237.54	$237.55	$237.50
Purchase #7	$103.48	8.112%	$111.8743	$111.87	$111.85	$111.90
7 purchase totals =	$1,161.89		$1,287.1029	$1,287.11	$1,287.10	$1,287.10