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	$91.93	6.142%	$97.5763	$97.58	$97.60	$97.60
Purchase #2	$29.71	8.609%	$32.2677	$32.27	$32.25	$32.30
Purchase #3	$138.58	12.748%	$156.2462	$156.25	$156.25	$156.20
Purchase #4	$74.43	5.713%	$78.6822	$78.68	$78.70	$78.70
Purchase #5	$178.59	5.710%	$188.7875	$188.79	$188.80	$188.80
Purchase #6	$176.59	10.131%	$194.4803	$194.48	$194.50	$194.50
Purchase #7	$227.77	10.462%	$251.5993	$251.60	$251.60	$251.60
7 purchase totals =	$917.60		$999.6395	$999.65	$999.70	$999.70