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	$189.47	5.253%	$199.4229	$199.42	$199.40	$199.40
Purchase #2	$173.71	7.420%	$186.5993	$186.60	$186.60	$186.60
Purchase #3	$9.46	10.176%	$10.4226	$10.42	$10.40	$10.40
Purchase #4	$130.34	10.583%	$144.1339	$144.13	$144.15	$144.10
Purchase #5	$95.27	7.511%	$102.4257	$102.43	$102.45	$102.40
Purchase #6	$196.87	5.740%	$208.1703	$208.17	$208.15	$208.20
Purchase #7	$206.78	12.776%	$233.1982	$233.20	$233.20	$233.20
7 purchase totals =	$1,001.90		$1,084.3729	$1,084.37	$1,084.35	$1,084.30