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	$35.39	3.160%	$36.5083	$36.51	$36.50	$36.50
Purchase #2	$147.29	4.602%	$154.0683	$154.07	$154.05	$154.10
Purchase #3	$248.69	13.757%	$282.9023	$282.90	$282.90	$282.90
Purchase #4	$78.25	5.653%	$82.6735	$82.67	$82.65	$82.70
Purchase #5	$172.55	13.686%	$196.1652	$196.17	$196.15	$196.20
Purchase #6	$208.46	8.110%	$225.3661	$225.37	$225.35	$225.40
Purchase #7	$223.47	6.827%	$238.7263	$238.73	$238.75	$238.70
7 purchase totals =	$1,114.10		$1,216.4100	$1,216.42	$1,216.35	$1,216.50