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	$213.39	4.158%	$222.2628	$222.26	$222.25	$222.30
Purchase #2	$142.32	12.817%	$160.5612	$160.56	$160.55	$160.60
Purchase #3	$38.50	9.749%	$42.2534	$42.25	$42.25	$42.30
Purchase #4	$50.42	8.126%	$54.5171	$54.52	$54.50	$54.50
Purchase #5	$55.41	10.340%	$61.1394	$61.14	$61.15	$61.10
Purchase #6	$175.72	4.397%	$183.4464	$183.45	$183.45	$183.40
Purchase #7	$67.68	13.153%	$76.582	$76.58	$76.60	$76.60
7 purchase totals =	$743.44		$800.7623	$800.76	$800.75	$800.80