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	$238.64	8.742%	$259.5019	$259.50	$259.50	$259.50
Purchase #2	$90.30	12.134%	$101.257	$101.26	$101.25	$101.30
Purchase #3	$38.78	5.603%	$40.9528	$40.95	$40.95	$41.00
Purchase #4	$36.74	12.823%	$41.4512	$41.45	$41.45	$41.50
Purchase #5	$223.84	7.720%	$241.1204	$241.12	$241.10	$241.10
Purchase #6	$210.73	3.189%	$217.4502	$217.45	$217.45	$217.50
Purchase #7	$96.25	3.608%	$99.7227	$99.72	$99.70	$99.70
7 purchase totals =	$935.28		$1,001.4562	$1,001.45	$1,001.40	$1,001.60