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	$100.79	12.509%	$113.3978	$113.40	$113.40	$113.40
Purchase #2	$85.32	4.725%	$89.3514	$89.35	$89.35	$89.40
Purchase #3	$197.50	4.672%	$206.7272	$206.73	$206.75	$206.70
Purchase #4	$113.62	3.812%	$117.9512	$117.95	$117.95	$118.00
Purchase #5	$79.55	12.491%	$89.4866	$89.49	$89.50	$89.50
Purchase #6	$164.59	8.408%	$178.4287	$178.43	$178.45	$178.40
Purchase #7	$197.97	3.501%	$204.9009	$204.90	$204.90	$204.90
7 purchase totals =	$939.34		$1,000.2438	$1,000.25	$1,000.30	$1,000.30