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	$233.58	3.548%	$241.8674	$241.87	$241.85	$241.90
Purchase #2	$187.55	11.724%	$209.5384	$209.54	$209.55	$209.50
Purchase #3	$22.91	7.233%	$24.5671	$24.57	$24.55	$24.60
Purchase #4	$244.67	12.148%	$274.3925	$274.39	$274.40	$274.40
Purchase #5	$14.33	5.544%	$15.1245	$15.12	$15.10	$15.10
Purchase #6	$226.72	6.500%	$241.4568	$241.46	$241.45	$241.50
Purchase #7	$51.56	9.625%	$56.5227	$56.52	$56.50	$56.50
7 purchase totals =	$981.32		$1,063.4694	$1,063.47	$1,063.40	$1,063.50