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	$148.90	10.395%	$164.3782	$164.38	$164.40	$164.40
Purchase #2	$16.49	7.285%	$17.6913	$17.69	$17.70	$17.70
Purchase #3	$56.85	9.528%	$62.2667	$62.27	$62.25	$62.30
Purchase #4	$135.63	4.369%	$141.5557	$141.56	$141.55	$141.60
Purchase #5	$156.62	10.202%	$172.5984	$172.60	$172.60	$172.60
Purchase #6	$248.40	7.279%	$266.481	$266.48	$266.50	$266.50
Purchase #7	$147.69	3.775%	$153.2653	$153.27	$153.25	$153.30
7 purchase totals =	$910.58		$978.2366	$978.25	$978.25	$978.40