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	$152.31	11.467%	$169.7754	$169.78	$169.80	$169.80
Purchase #2	$80.90	6.864%	$86.453	$86.45	$86.45	$86.50
Purchase #3	$207.98	13.186%	$235.4042	$235.40	$235.40	$235.40
Purchase #4	$169.96	3.656%	$176.1737	$176.17	$176.15	$176.20
Purchase #5	$160.43	4.645%	$167.882	$167.88	$167.90	$167.90
Purchase #6	$228.64	11.703%	$255.3977	$255.40	$255.40	$255.40
Purchase #7	$205.63	5.732%	$217.4167	$217.42	$217.40	$217.40
7 purchase totals =	$1,205.85		$1,308.5027	$1,308.50	$1,308.50	$1,308.60