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	$20.85	5.295%	$21.954	$21.95	$21.95	$22.00
Purchase #2	$197.40	10.690%	$218.5021	$218.50	$218.50	$218.50
Purchase #3	$191.74	7.756%	$206.6114	$206.61	$206.60	$206.60
Purchase #4	$27.32	7.653%	$29.4108	$29.41	$29.40	$29.40
Purchase #5	$147.48	7.678%	$158.8035	$158.80	$158.80	$158.80
Purchase #6	$152.55	5.446%	$160.8579	$160.86	$160.85	$160.90
Purchase #7	$86.47	4.575%	$90.426	$90.43	$90.45	$90.40
7 purchase totals =	$823.81		$886.5657	$886.56	$886.55	$886.60