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	$33.94	9.767%	$37.2549	$37.25	$37.25	$37.30
Purchase #2	$239.72	6.528%	$255.3689	$255.37	$255.35	$255.40
Purchase #3	$232.48	12.237%	$260.9286	$260.93	$260.95	$260.90
Purchase #4	$237.27	12.236%	$266.3024	$266.30	$266.30	$266.30
Purchase #5	$97.50	13.443%	$110.6069	$110.61	$110.60	$110.60
Purchase #6	$146.46	4.349%	$152.8295	$152.83	$152.85	$152.80
Purchase #7	$5.51	5.565%	$5.8166	$5.82	$5.80	$5.80
7 purchase totals =	$992.88		$1,089.1078	$1,089.11	$1,089.10	$1,089.10