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	$173.25	13.380%	$196.4309	$196.43	$196.45	$196.40
Purchase #2	$51.77	12.144%	$58.0569	$58.06	$58.05	$58.10
Purchase #3	$94.97	7.672%	$102.2561	$102.26	$102.25	$102.30
Purchase #4	$110.28	12.245%	$123.7838	$123.78	$123.80	$123.80
Purchase #5	$250.58	9.683%	$274.8437	$274.84	$274.85	$274.80
Purchase #6	$213.52	8.124%	$230.8664	$230.87	$230.85	$230.90
Purchase #7	$91.45	5.487%	$96.4679	$96.47	$96.45	$96.50
7 purchase totals =	$985.82		$1,082.7057	$1,082.71	$1,082.70	$1,082.80