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	$168.71	7.431%	$181.2468	$181.25	$181.25	$181.20
Purchase #2	$24.47	12.862%	$27.6173	$27.62	$27.60	$27.60
Purchase #3	$77.56	5.725%	$82.0003	$82.00	$82.00	$82.00
Purchase #4	$33.60	10.622%	$37.169	$37.17	$37.15	$37.20
Purchase #5	$171.28	10.390%	$189.076	$189.08	$189.10	$189.10
Purchase #6	$211.43	5.661%	$223.3991	$223.40	$223.40	$223.40
Purchase #7	$218.87	9.327%	$239.284	$239.28	$239.30	$239.30
7 purchase totals =	$905.92		$979.7925	$979.80	$979.80	$979.80