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	$32.71	6.142%	$34.719	$34.72	$34.70	$34.70
Purchase #2	$220.90	10.617%	$244.353	$244.35	$244.35	$244.40
Purchase #3	$147.54	13.822%	$167.933	$167.93	$167.95	$167.90
Purchase #4	$37.28	3.376%	$38.5386	$38.54	$38.55	$38.50
Purchase #5	$146.85	5.448%	$154.8504	$154.85	$154.85	$154.90
Purchase #6	$179.25	6.307%	$190.5553	$190.56	$190.55	$190.60
Purchase #7	$232.64	11.545%	$259.4983	$259.50	$259.50	$259.50
7 purchase totals =	$997.17		$1,090.4476	$1,090.45	$1,090.45	$1,090.50