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	$228.62	3.681%	$237.0355	$237.04	$237.05	$237.00
Purchase #2	$185.56	5.431%	$195.6378	$195.64	$195.65	$195.60
Purchase #3	$63.89	13.169%	$72.3037	$72.30	$72.30	$72.30
Purchase #4	$36.95	5.763%	$39.0794	$39.08	$39.10	$39.10
Purchase #5	$19.30	5.543%	$20.3698	$20.37	$20.35	$20.40
Purchase #6	$36.47	6.558%	$38.8617	$38.86	$38.85	$38.90
Purchase #7	$39.71	8.602%	$43.1259	$43.13	$43.15	$43.10
7 purchase totals =	$610.50		$646.4138	$646.42	$646.45	$646.40