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	$89.98	13.760%	$102.3612	$102.36	$102.35	$102.40
Purchase #2	$157.81	5.577%	$166.6111	$166.61	$166.60	$166.60
Purchase #3	$11.47	11.793%	$12.8227	$12.82	$12.80	$12.80
Purchase #4	$46.98	13.711%	$53.4214	$53.42	$53.40	$53.40
Purchase #5	$203.36	8.517%	$220.6802	$220.68	$220.70	$220.70
Purchase #6	$112.42	13.706%	$127.8283	$127.83	$127.85	$127.80
Purchase #7	$90.40	11.324%	$100.6369	$100.64	$100.65	$100.60
7 purchase totals =	$712.42		$784.3618	$784.36	$784.35	$784.30