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	$141.39	9.239%	$154.453	$154.45	$154.45	$154.50
Purchase #2	$144.75	5.801%	$153.1469	$153.15	$153.15	$153.10
Purchase #3	$91.69	4.460%	$95.7794	$95.78	$95.80	$95.80
Purchase #4	$61.55	9.495%	$67.3942	$67.39	$67.40	$67.40
Purchase #5	$88.70	3.531%	$91.832	$91.83	$91.85	$91.80
Purchase #6	$135.99	4.748%	$142.4468	$142.45	$142.45	$142.40
Purchase #7	$169.34	9.467%	$185.3714	$185.37	$185.35	$185.40
7 purchase totals =	$833.41		$890.4237	$890.42	$890.45	$890.40