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	$76.90	7.410%	$82.5983	$82.60	$82.60	$82.60
Purchase #2	$187.38	11.106%	$208.1904	$208.19	$208.20	$208.20
Purchase #3	$217.67	5.525%	$229.6963	$229.70	$229.70	$229.70
Purchase #4	$198.38	12.146%	$222.4752	$222.48	$222.50	$222.50
Purchase #5	$164.84	4.578%	$172.3864	$172.39	$172.40	$172.40
Purchase #6	$19.62	9.613%	$21.5061	$21.51	$21.50	$21.50
Purchase #7	$242.84	12.267%	$272.6292	$272.63	$272.65	$272.60
7 purchase totals =	$1,107.63		$1,209.4819	$1,209.50	$1,209.55	$1,209.50