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	$82.80	10.255%	$91.2911	$91.29	$91.30	$91.30
Purchase #2	$217.61	3.610%	$225.4657	$225.47	$225.45	$225.50
Purchase #3	$125.86	3.707%	$130.5256	$130.53	$130.55	$130.50
Purchase #4	$73.79	10.751%	$81.7232	$81.72	$81.70	$81.70
Purchase #5	$176.48	11.403%	$196.604	$196.60	$196.60	$196.60
Purchase #6	$108.39	4.617%	$113.3944	$113.39	$113.40	$113.40
Purchase #7	$59.86	5.344%	$63.0589	$63.06	$63.05	$63.10
7 purchase totals =	$844.79		$902.0629	$902.06	$902.05	$902.10