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	$114.74	11.241%	$127.6379	$127.64	$127.65	$127.60
Purchase #2	$215.50	3.716%	$223.508	$223.51	$223.50	$223.50
Purchase #3	$123.72	3.395%	$127.9203	$127.92	$127.90	$127.90
Purchase #4	$246.58	4.386%	$257.395	$257.40	$257.40	$257.40
Purchase #5	$81.68	10.340%	$90.1257	$90.13	$90.15	$90.10
Purchase #6	$27.26	6.640%	$29.0701	$29.07	$29.05	$29.10
Purchase #7	$19.78	5.315%	$20.8313	$20.83	$20.85	$20.80
7 purchase totals =	$829.26		$876.4883	$876.50	$876.50	$876.40