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	$158.90	8.822%	$172.9182	$172.92	$172.90	$172.90
Purchase #2	$135.67	13.284%	$153.6924	$153.69	$153.70	$153.70
Purchase #3	$205.92	12.625%	$231.9174	$231.92	$231.90	$231.90
Purchase #4	$18.63	13.777%	$21.1967	$21.20	$21.20	$21.20
Purchase #5	$134.58	12.434%	$151.3137	$151.31	$151.30	$151.30
Purchase #6	$70.38	3.403%	$72.775	$72.78	$72.80	$72.80
Purchase #7	$213.89	5.580%	$225.8251	$225.83	$225.85	$225.80
7 purchase totals =	$937.97		$1,029.6385	$1,029.65	$1,029.65	$1,029.60