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	$90.54	5.580%	$95.5921	$95.59	$95.60	$95.60
Purchase #2	$92.89	10.556%	$102.6955	$102.70	$102.70	$102.70
Purchase #3	$44.74	4.777%	$46.8772	$46.88	$46.90	$46.90
Purchase #4	$38.40	4.411%	$40.0938	$40.09	$40.10	$40.10
Purchase #5	$178.68	7.202%	$191.5485	$191.55	$191.55	$191.50
Purchase #6	$141.45	7.119%	$151.5198	$151.52	$151.50	$151.50
Purchase #7	$99.40	7.515%	$106.8699	$106.87	$106.85	$106.90
7 purchase totals =	$686.10		$735.1968	$735.20	$735.20	$735.20