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	$103.40	9.852%	$113.587	$113.59	$113.60	$113.60
Purchase #2	$55.33	7.466%	$59.4609	$59.46	$59.45	$59.50
Purchase #3	$247.49	13.874%	$281.8268	$281.83	$281.85	$281.80
Purchase #4	$48.97	11.760%	$54.7289	$54.73	$54.75	$54.70
Purchase #5	$249.74	12.227%	$280.2757	$280.28	$280.30	$280.30
Purchase #6	$146.59	6.177%	$155.6449	$155.64	$155.65	$155.60
Purchase #7	$19.86	10.814%	$22.0077	$22.01	$22.00	$22.00
7 purchase totals =	$871.38		$967.5319	$967.54	$967.60	$967.50