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	$72.79	13.483%	$82.6043	$82.60	$82.60	$82.60
Purchase #2	$78.42	9.443%	$85.8252	$85.83	$85.85	$85.80
Purchase #3	$15.54	4.714%	$16.2726	$16.27	$16.25	$16.30
Purchase #4	$174.76	3.782%	$181.3694	$181.37	$181.35	$181.40
Purchase #5	$167.43	3.779%	$173.7572	$173.76	$173.75	$173.80
Purchase #6	$22.34	10.838%	$24.7612	$24.76	$24.75	$24.80
Purchase #7	$53.73	8.326%	$58.2036	$58.20	$58.20	$58.20
7 purchase totals =	$585.01		$622.7935	$622.79	$622.75	$622.90