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	$176.72	8.416%	$191.5928	$191.59	$191.60	$191.60
Purchase #2	$61.31	7.738%	$66.0542	$66.05	$66.05	$66.10
Purchase #3	$132.99	11.607%	$148.4261	$148.43	$148.45	$148.40
Purchase #4	$205.73	7.834%	$221.8469	$221.85	$221.85	$221.80
Purchase #5	$74.47	10.732%	$82.4621	$82.46	$82.45	$82.50
Purchase #6	$31.43	5.194%	$33.0625	$33.06	$33.05	$33.10
Purchase #7	$203.68	13.550%	$231.2786	$231.28	$231.30	$231.30
7 purchase totals =	$886.33		$974.7232	$974.72	$974.75	$974.80