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	$76.62	8.725%	$83.3051	$83.31	$83.30	$83.30
Purchase #2	$95.86	7.773%	$103.3112	$103.31	$103.30	$103.30
Purchase #3	$137.75	8.837%	$149.923	$149.92	$149.90	$149.90
Purchase #4	$82.60	10.719%	$91.4539	$91.45	$91.45	$91.50
Purchase #5	$218.64	4.662%	$228.833	$228.83	$228.85	$228.80
Purchase #6	$207.98	9.580%	$227.9045	$227.90	$227.90	$227.90
Purchase #7	$196.82	9.666%	$215.8446	$215.84	$215.85	$215.80
7 purchase totals =	$1,016.27		$1,100.5753	$1,100.56	$1,100.55	$1,100.50