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	$97.85	5.740%	$103.4666	$103.47	$103.45	$103.50
Purchase #2	$47.37	4.176%	$49.3482	$49.35	$49.35	$49.30
Purchase #3	$132.29	8.416%	$143.4235	$143.42	$143.40	$143.40
Purchase #4	$245.89	3.145%	$253.6232	$253.62	$253.60	$253.60
Purchase #5	$63.30	4.132%	$65.9156	$65.92	$65.90	$65.90
Purchase #6	$99.80	8.754%	$108.5365	$108.54	$108.55	$108.50
Purchase #7	$212.83	7.525%	$228.8455	$228.85	$228.85	$228.80
7 purchase totals =	$899.33		$953.1591	$953.17	$953.10	$953.00