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	$83.38	8.436%	$90.4139	$90.41	$90.40	$90.40
Purchase #2	$165.79	5.397%	$174.7377	$174.74	$174.75	$174.70
Purchase #3	$208.64	4.194%	$217.3904	$217.39	$217.40	$217.40
Purchase #4	$200.83	5.842%	$212.5625	$212.56	$212.55	$212.60
Purchase #5	$193.34	11.462%	$215.5006	$215.50	$215.50	$215.50
Purchase #6	$36.78	13.117%	$41.6044	$41.60	$41.60	$41.60
Purchase #7	$173.53	3.373%	$179.3832	$179.38	$179.40	$179.40
7 purchase totals =	$1,062.29		$1,131.5927	$1,131.58	$1,131.60	$1,131.60