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	$231.35	13.487%	$262.5522	$262.55	$262.55	$262.60
Purchase #2	$42.25	4.579%	$44.1846	$44.18	$44.20	$44.20
Purchase #3	$174.90	12.536%	$196.8255	$196.83	$196.85	$196.80
Purchase #4	$39.71	4.625%	$41.5466	$41.55	$41.55	$41.50
Purchase #5	$211.64	4.194%	$220.5162	$220.52	$220.50	$220.50
Purchase #6	$85.60	6.517%	$91.1786	$91.18	$91.20	$91.20
Purchase #7	$217.37	10.840%	$240.9329	$240.93	$240.95	$240.90
7 purchase totals =	$1,002.82		$1,097.7366	$1,097.74	$1,097.80	$1,097.70