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	$217.68	8.656%	$236.5224	$236.52	$236.50	$236.50
Purchase #2	$74.27	11.517%	$82.8237	$82.82	$82.80	$82.80
Purchase #3	$67.42	5.637%	$71.2205	$71.22	$71.20	$71.20
Purchase #4	$159.49	8.469%	$172.9972	$173.00	$173.00	$173.00
Purchase #5	$119.55	6.671%	$127.5252	$127.53	$127.55	$127.50
Purchase #6	$108.72	12.631%	$122.4524	$122.45	$122.45	$122.50
Purchase #7	$180.90	6.154%	$192.0326	$192.03	$192.05	$192.00
7 purchase totals =	$928.03		$1,005.5740	$1,005.57	$1,005.55	$1,005.50