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	$15.93	3.830%	$16.5401	$16.54	$16.55	$16.50
Purchase #2	$68.85	5.377%	$72.5521	$72.55	$72.55	$72.60
Purchase #3	$203.43	5.778%	$215.1842	$215.18	$215.20	$215.20
Purchase #4	$41.33	4.234%	$43.0799	$43.08	$43.10	$43.10
Purchase #5	$31.51	5.672%	$33.2972	$33.30	$33.30	$33.30
Purchase #6	$157.37	11.826%	$175.9806	$175.98	$176.00	$176.00
Purchase #7	$158.30	9.422%	$173.215	$173.22	$173.20	$173.20
7 purchase totals =	$676.72		$729.8491	$729.85	$729.90	$729.90