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	$125.62	11.340%	$139.8653	$139.87	$139.85	$139.90
Purchase #2	$175.88	8.370%	$190.6012	$190.60	$190.60	$190.60
Purchase #3	$147.37	7.772%	$158.8236	$158.82	$158.80	$158.80
Purchase #4	$91.30	13.338%	$103.4776	$103.48	$103.50	$103.50
Purchase #5	$192.68	4.365%	$201.0905	$201.09	$201.10	$201.10
Purchase #6	$172.30	11.335%	$191.8302	$191.83	$191.85	$191.80
Purchase #7	$29.37	7.805%	$31.6623	$31.66	$31.65	$31.70
7 purchase totals =	$934.52		$1,017.3507	$1,017.35	$1,017.35	$1,017.40