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	$151.36	8.703%	$164.5329	$164.53	$164.55	$164.50
Purchase #2	$142.64	8.579%	$154.8771	$154.88	$154.90	$154.90
Purchase #3	$80.57	3.209%	$83.1555	$83.16	$83.15	$83.20
Purchase #4	$114.93	11.603%	$128.2653	$128.27	$128.25	$128.30
Purchase #5	$44.36	8.483%	$48.1231	$48.12	$48.10	$48.10
Purchase #6	$131.34	11.371%	$146.2747	$146.27	$146.25	$146.30
Purchase #7	$35.52	11.308%	$39.5366	$39.54	$39.55	$39.50
7 purchase totals =	$700.72		$764.7652	$764.77	$764.75	$764.80