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	$30.92	9.138%	$33.7455	$33.75	$33.75	$33.70
Purchase #2	$14.69	7.260%	$15.7565	$15.76	$15.75	$15.80
Purchase #3	$24.48	11.260%	$27.2364	$27.24	$27.25	$27.20
Purchase #4	$59.87	9.753%	$65.7091	$65.71	$65.70	$65.70
Purchase #5	$137.42	5.130%	$144.4696	$144.47	$144.45	$144.50
Purchase #6	$97.51	11.351%	$108.5784	$108.58	$108.60	$108.60
Purchase #7	$82.42	9.584%	$90.3191	$90.32	$90.30	$90.30
7 purchase totals =	$447.31		$485.8146	$485.83	$485.80	$485.80