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	$249.52	5.312%	$262.7745	$262.77	$262.75	$262.80
Purchase #2	$74.45	10.704%	$82.4191	$82.42	$82.40	$82.40
Purchase #3	$227.54	9.119%	$248.2894	$248.29	$248.30	$248.30
Purchase #4	$140.27	13.443%	$159.1265	$159.13	$159.15	$159.10
Purchase #5	$134.68	5.229%	$141.7224	$141.72	$141.70	$141.70
Purchase #6	$110.72	5.472%	$116.7786	$116.78	$116.80	$116.80
Purchase #7	$84.89	6.657%	$90.5411	$90.54	$90.55	$90.50
7 purchase totals =	$1,022.07		$1,101.6516	$1,101.65	$1,101.65	$1,101.60