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	$205.98	13.561%	$233.9129	$233.91	$233.90	$233.90
Purchase #2	$18.99	9.139%	$20.7255	$20.73	$20.75	$20.70
Purchase #3	$101.28	12.826%	$114.2702	$114.27	$114.25	$114.30
Purchase #4	$59.41	5.852%	$62.8867	$62.89	$62.90	$62.90
Purchase #5	$28.93	12.546%	$32.5596	$32.56	$32.55	$32.60
Purchase #6	$48.83	4.635%	$51.0933	$51.09	$51.10	$51.10
Purchase #7	$100.34	10.130%	$110.5044	$110.50	$110.50	$110.50
7 purchase totals =	$563.76		$625.9526	$625.95	$625.95	$626.00