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	$92.86	12.828%	$104.7721	$104.77	$104.75	$104.80
Purchase #2	$161.77	12.651%	$182.2355	$182.24	$182.25	$182.20
Purchase #3	$141.40	8.623%	$153.5929	$153.59	$153.60	$153.60
Purchase #4	$249.35	4.139%	$259.6706	$259.67	$259.65	$259.70
Purchase #5	$249.86	12.410%	$280.8676	$280.87	$280.85	$280.90
Purchase #6	$108.77	8.763%	$118.3015	$118.30	$118.30	$118.30
Purchase #7	$24.87	13.495%	$28.2262	$28.23	$28.25	$28.20
7 purchase totals =	$1,028.88		$1,127.6664	$1,127.67	$1,127.65	$1,127.70