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	$202.29	5.421%	$213.2561	$213.26	$213.25	$213.30
Purchase #2	$192.51	5.246%	$202.6091	$202.61	$202.60	$202.60
Purchase #3	$99.56	4.208%	$103.7495	$103.75	$103.75	$103.70
Purchase #4	$150.29	3.383%	$155.3743	$155.37	$155.35	$155.40
Purchase #5	$70.28	11.662%	$78.4761	$78.48	$78.50	$78.50
Purchase #6	$44.33	3.379%	$45.8279	$45.83	$45.85	$45.80
Purchase #7	$21.91	10.553%	$24.2222	$24.22	$24.20	$24.20
7 purchase totals =	$781.17		$823.5152	$823.52	$823.50	$823.50