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	$123.33	11.686%	$137.7423	$137.74	$137.75	$137.70
Purchase #2	$151.42	3.150%	$156.1897	$156.19	$156.20	$156.20
Purchase #3	$87.59	13.589%	$99.4926	$99.49	$99.50	$99.50
Purchase #4	$159.76	7.730%	$172.1094	$172.11	$172.10	$172.10
Purchase #5	$224.61	13.540%	$255.0222	$255.02	$255.00	$255.00
Purchase #6	$144.86	9.542%	$158.6825	$158.68	$158.70	$158.70
Purchase #7	$20.30	7.194%	$21.7604	$21.76	$21.75	$21.80
7 purchase totals =	$911.87		$1,000.9991	$1,000.99	$1,001.00	$1,001.00