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	$94.82	10.342%	$104.6263	$104.63	$104.65	$104.60
Purchase #2	$178.44	10.307%	$196.8318	$196.83	$196.85	$196.80
Purchase #3	$167.36	3.170%	$172.6653	$172.67	$172.65	$172.70
Purchase #4	$29.33	11.178%	$32.6085	$32.61	$32.60	$32.60
Purchase #5	$142.64	5.302%	$150.2028	$150.20	$150.20	$150.20
Purchase #6	$189.95	13.516%	$215.6236	$215.62	$215.60	$215.60
Purchase #7	$240.42	7.176%	$257.6725	$257.67	$257.65	$257.70
7 purchase totals =	$1,042.96		$1,130.2308	$1,130.23	$1,130.20	$1,130.20