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	$175.78	13.696%	$199.8548	$199.85	$199.85	$199.90
Purchase #2	$224.75	12.852%	$253.6349	$253.63	$253.65	$253.60
Purchase #3	$144.77	3.826%	$150.3089	$150.31	$150.30	$150.30
Purchase #4	$19.34	12.829%	$21.8211	$21.82	$21.80	$21.80
Purchase #5	$186.55	7.659%	$200.8379	$200.84	$200.85	$200.80
Purchase #6	$66.90	8.503%	$72.5885	$72.59	$72.60	$72.60
Purchase #7	$219.45	13.403%	$248.8629	$248.86	$248.85	$248.90
7 purchase totals =	$1,037.54		$1,147.9090	$1,147.90	$1,147.90	$1,147.90