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	$96.98	6.540%	$103.3225	$103.32	$103.30	$103.30
Purchase #2	$42.47	6.471%	$45.2182	$45.22	$45.20	$45.20
Purchase #3	$145.52	13.153%	$164.6602	$164.66	$164.65	$164.70
Purchase #4	$45.53	6.734%	$48.596	$48.60	$48.60	$48.60
Purchase #5	$59.73	6.752%	$63.763	$63.76	$63.75	$63.80
Purchase #6	$178.74	5.616%	$188.778	$188.78	$188.80	$188.80
Purchase #7	$222.74	5.122%	$234.1487	$234.15	$234.15	$234.10
7 purchase totals =	$791.71		$848.4866	$848.49	$848.45	$848.50