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	$120.77	11.314%	$134.4339	$134.43	$134.45	$134.40
Purchase #2	$165.38	5.289%	$174.1269	$174.13	$174.15	$174.10
Purchase #3	$246.56	3.456%	$255.0811	$255.08	$255.10	$255.10
Purchase #4	$150.32	11.659%	$167.8458	$167.85	$167.85	$167.80
Purchase #5	$219.37	7.627%	$236.1013	$236.10	$236.10	$236.10
Purchase #6	$94.48	5.683%	$99.8493	$99.85	$99.85	$99.80
Purchase #7	$102.75	10.341%	$113.3754	$113.38	$113.40	$113.40
7 purchase totals =	$1,099.63		$1,180.8137	$1,180.82	$1,180.90	$1,180.70