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	$199.77	11.774%	$223.2909	$223.29	$223.30	$223.30
Purchase #2	$160.27	4.567%	$167.5895	$167.59	$167.60	$167.60
Purchase #3	$49.32	12.407%	$55.4391	$55.44	$55.45	$55.40
Purchase #4	$113.95	11.456%	$127.0041	$127.00	$127.00	$127.00
Purchase #5	$53.83	13.659%	$61.1826	$61.18	$61.20	$61.20
Purchase #6	$193.40	10.124%	$212.9798	$212.98	$213.00	$213.00
Purchase #7	$92.52	8.245%	$100.1483	$100.15	$100.15	$100.10
7 purchase totals =	$863.06		$947.6343	$947.63	$947.70	$947.60