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	$247.80	3.726%	$257.033	$257.03	$257.05	$257.00
Purchase #2	$30.43	4.608%	$31.8322	$31.83	$31.85	$31.80
Purchase #3	$176.43	4.831%	$184.9533	$184.95	$184.95	$185.00
Purchase #4	$165.92	7.747%	$178.7738	$178.77	$178.75	$178.80
Purchase #5	$112.77	13.417%	$127.9004	$127.90	$127.90	$127.90
Purchase #6	$219.25	6.381%	$233.2403	$233.24	$233.25	$233.20
Purchase #7	$50.54	6.554%	$53.8524	$53.85	$53.85	$53.90
7 purchase totals =	$1,003.14		$1,067.5854	$1,067.57	$1,067.60	$1,067.60