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	$9.62	4.269%	$10.0307	$10.03	$10.05	$10.00
Purchase #2	$45.59	9.166%	$49.7688	$49.77	$49.75	$49.80
Purchase #3	$22.39	13.870%	$25.4955	$25.50	$25.50	$25.50
Purchase #4	$52.38	7.140%	$56.1199	$56.12	$56.10	$56.10
Purchase #5	$18.82	12.265%	$21.1283	$21.13	$21.15	$21.10
Purchase #6	$145.88	8.410%	$158.1485	$158.15	$158.15	$158.10
Purchase #7	$39.55	12.215%	$44.381	$44.38	$44.40	$44.40
7 purchase totals =	$334.23		$365.0727	$365.08	$365.10	$365.00