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	$140.28	7.424%	$150.6944	$150.69	$150.70	$150.70
Purchase #2	$8.76	5.398%	$9.2329	$9.23	$9.25	$9.20
Purchase #3	$157.99	7.141%	$169.2721	$169.27	$169.25	$169.30
Purchase #4	$59.25	6.468%	$63.0823	$63.08	$63.10	$63.10
Purchase #5	$173.83	6.534%	$185.1881	$185.19	$185.20	$185.20
Purchase #6	$141.35	8.105%	$152.8064	$152.81	$152.80	$152.80
Purchase #7	$83.32	8.210%	$90.1606	$90.16	$90.15	$90.20
7 purchase totals =	$764.78		$820.4368	$820.43	$820.45	$820.50