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	$102.26	9.749%	$112.2293	$112.23	$112.25	$112.20
Purchase #2	$59.94	9.825%	$65.8291	$65.83	$65.85	$65.80
Purchase #3	$158.91	10.241%	$175.184	$175.18	$175.20	$175.20
Purchase #4	$118.30	12.350%	$132.9101	$132.91	$132.90	$132.90
Purchase #5	$29.95	8.273%	$32.4278	$32.43	$32.45	$32.40
Purchase #6	$32.47	4.234%	$33.8448	$33.84	$33.85	$33.80
Purchase #7	$200.86	13.478%	$227.9319	$227.93	$227.95	$227.90
7 purchase totals =	$702.69		$780.3570	$780.35	$780.45	$780.20