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	$73.55	12.174%	$82.504	$82.50	$82.50	$82.50
Purchase #2	$148.65	9.372%	$162.5815	$162.58	$162.60	$162.60
Purchase #3	$228.93	12.122%	$256.6809	$256.68	$256.70	$256.70
Purchase #4	$210.33	12.809%	$237.2712	$237.27	$237.25	$237.30
Purchase #5	$11.31	5.197%	$11.8978	$11.90	$11.90	$11.90
Purchase #6	$192.79	11.509%	$214.9782	$214.98	$215.00	$215.00
Purchase #7	$101.47	13.697%	$115.3683	$115.37	$115.35	$115.40
7 purchase totals =	$967.03		$1,081.2819	$1,081.28	$1,081.30	$1,081.40