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	$242.42	8.374%	$262.7203	$262.72	$262.70	$262.70
Purchase #2	$193.83	3.523%	$200.6586	$200.66	$200.65	$200.70
Purchase #3	$159.85	4.740%	$167.4269	$167.43	$167.45	$167.40
Purchase #4	$84.46	13.112%	$95.5344	$95.53	$95.55	$95.50
Purchase #5	$225.37	13.271%	$255.2789	$255.28	$255.30	$255.30
Purchase #6	$186.94	6.144%	$198.4256	$198.43	$198.45	$198.40
Purchase #7	$38.35	6.796%	$40.9563	$40.96	$40.95	$41.00
7 purchase totals =	$1,131.22		$1,221.0010	$1,221.01	$1,221.05	$1,221.00