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	$89.45	13.227%	$101.2816	$101.28	$101.30	$101.30
Purchase #2	$59.74	6.492%	$63.6183	$63.62	$63.60	$63.60
Purchase #3	$54.28	9.496%	$59.4344	$59.43	$59.45	$59.40
Purchase #4	$63.32	13.725%	$72.0107	$72.01	$72.00	$72.00
Purchase #5	$155.47	9.122%	$169.652	$169.65	$169.65	$169.70
Purchase #6	$42.52	13.542%	$48.2781	$48.28	$48.30	$48.30
Purchase #7	$158.88	11.505%	$177.1591	$177.16	$177.15	$177.20
7 purchase totals =	$623.66		$691.4342	$691.43	$691.45	$691.50