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	$161.54	3.781%	$167.6478	$167.65	$167.65	$167.60
Purchase #2	$159.56	13.709%	$181.4341	$181.43	$181.45	$181.40
Purchase #3	$143.86	5.868%	$152.3017	$152.30	$152.30	$152.30
Purchase #4	$189.83	3.162%	$195.8324	$195.83	$195.85	$195.80
Purchase #5	$180.70	5.481%	$190.6042	$190.60	$190.60	$190.60
Purchase #6	$113.87	9.178%	$124.321	$124.32	$124.30	$124.30
Purchase #7	$191.59	4.623%	$200.4472	$200.45	$200.45	$200.40
7 purchase totals =	$1,140.95		$1,212.5884	$1,212.58	$1,212.60	$1,212.40