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	$190.35	3.273%	$196.5802	$196.58	$196.60	$196.60
Purchase #2	$20.35	9.863%	$22.3571	$22.36	$22.35	$22.40
Purchase #3	$111.30	3.263%	$114.9317	$114.93	$114.95	$114.90
Purchase #4	$53.42	3.848%	$55.4756	$55.48	$55.50	$55.50
Purchase #5	$196.43	5.451%	$207.1374	$207.14	$207.15	$207.10
Purchase #6	$140.55	13.194%	$159.0942	$159.09	$159.10	$159.10
Purchase #7	$226.48	8.871%	$246.571	$246.57	$246.55	$246.60
7 purchase totals =	$938.88		$1,002.1472	$1,002.15	$1,002.20	$1,002.20