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	$152.66	13.327%	$173.005	$173.01	$173.00	$173.00
Purchase #2	$196.67	8.784%	$213.9455	$213.95	$213.95	$213.90
Purchase #3	$89.71	12.416%	$100.8484	$100.85	$100.85	$100.80
Purchase #4	$141.97	6.689%	$151.4664	$151.47	$151.45	$151.50
Purchase #5	$209.51	5.140%	$220.2788	$220.28	$220.30	$220.30
Purchase #6	$40.60	4.826%	$42.5594	$42.56	$42.55	$42.60
Purchase #7	$134.44	12.288%	$150.96	$150.96	$150.95	$151.00
7 purchase totals =	$965.56		$1,053.0635	$1,053.08	$1,053.05	$1,053.10