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	$145.80	13.168%	$164.9989	$165.00	$165.00	$165.00
Purchase #2	$211.43	7.719%	$227.7503	$227.75	$227.75	$227.80
Purchase #3	$239.91	6.618%	$255.7872	$255.79	$255.80	$255.80
Purchase #4	$142.32	4.371%	$148.5408	$148.54	$148.55	$148.50
Purchase #5	$29.45	13.484%	$33.421	$33.42	$33.40	$33.40
Purchase #6	$207.34	6.772%	$221.3811	$221.38	$221.40	$221.40
Purchase #7	$105.60	3.760%	$109.5706	$109.57	$109.55	$109.60
7 purchase totals =	$1,081.85		$1,161.4499	$1,161.45	$1,161.45	$1,161.50