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	$136.75	5.694%	$144.5365	$144.54	$144.55	$144.50
Purchase #2	$104.31	11.797%	$116.6155	$116.62	$116.60	$116.60
Purchase #3	$248.83	10.590%	$275.1811	$275.18	$275.20	$275.20
Purchase #4	$17.44	7.746%	$18.7909	$18.79	$18.80	$18.80
Purchase #5	$236.63	9.229%	$258.4686	$258.47	$258.45	$258.50
Purchase #6	$166.76	11.349%	$185.6856	$185.69	$185.70	$185.70
Purchase #7	$98.81	4.631%	$103.3859	$103.39	$103.40	$103.40
7 purchase totals =	$1,009.53		$1,102.6641	$1,102.68	$1,102.70	$1,102.70