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	$174.87	13.768%	$198.9461	$198.95	$198.95	$198.90
Purchase #2	$102.85	6.703%	$109.744	$109.74	$109.75	$109.70
Purchase #3	$226.25	13.136%	$255.9702	$255.97	$255.95	$256.00
Purchase #4	$87.85	9.147%	$95.8856	$95.89	$95.90	$95.90
Purchase #5	$136.59	4.823%	$143.1777	$143.18	$143.20	$143.20
Purchase #6	$175.60	5.580%	$185.3985	$185.40	$185.40	$185.40
Purchase #7	$100.83	9.499%	$110.4078	$110.41	$110.40	$110.40
7 purchase totals =	$1,004.84		$1,099.5299	$1,099.54	$1,099.55	$1,099.50