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	$69.37	11.543%	$77.3774	$77.38	$77.40	$77.40
Purchase #2	$70.78	10.634%	$78.3067	$78.31	$78.30	$78.30
Purchase #3	$158.92	10.739%	$175.9864	$175.99	$176.00	$176.00
Purchase #4	$125.50	4.528%	$131.1826	$131.18	$131.20	$131.20
Purchase #5	$96.49	13.248%	$109.273	$109.27	$109.25	$109.30
Purchase #6	$55.42	12.782%	$62.5038	$62.50	$62.50	$62.50
Purchase #7	$62.55	8.185%	$67.6697	$67.67	$67.65	$67.70
7 purchase totals =	$639.03		$702.2996	$702.30	$702.30	$702.40