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	$98.59	13.572%	$111.9706	$111.97	$111.95	$112.00
Purchase #2	$123.61	7.762%	$133.2046	$133.20	$133.20	$133.20
Purchase #3	$57.48	11.393%	$64.0287	$64.03	$64.05	$64.00
Purchase #4	$92.85	8.536%	$100.7757	$100.78	$100.80	$100.80
Purchase #5	$221.95	7.506%	$238.6096	$238.61	$238.60	$238.60
Purchase #6	$162.36	13.240%	$183.8565	$183.86	$183.85	$183.90
Purchase #7	$42.45	13.828%	$48.32	$48.32	$48.30	$48.30
7 purchase totals =	$799.29		$880.7657	$880.77	$880.75	$880.80