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	$56.71	8.315%	$61.4254	$61.43	$61.45	$61.40
Purchase #2	$108.56	13.853%	$123.5988	$123.60	$123.60	$123.60
Purchase #3	$12.64	13.844%	$14.3899	$14.39	$14.40	$14.40
Purchase #4	$62.47	6.108%	$66.2857	$66.29	$66.30	$66.30
Purchase #5	$14.81	5.121%	$15.5684	$15.57	$15.55	$15.60
Purchase #6	$104.88	3.412%	$108.4585	$108.46	$108.45	$108.50
Purchase #7	$5.42	11.375%	$6.0365	$6.04	$6.05	$6.00
7 purchase totals =	$365.49		$395.7632	$395.78	$395.80	$395.80