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	$215.94	3.228%	$222.9105	$222.91	$222.90	$222.90
Purchase #2	$172.50	5.245%	$181.5476	$181.55	$181.55	$181.50
Purchase #3	$231.82	5.187%	$243.8445	$243.84	$243.85	$243.80
Purchase #4	$35.86	6.517%	$38.197	$38.20	$38.20	$38.20
Purchase #5	$35.81	7.372%	$38.4499	$38.45	$38.45	$38.40
Purchase #6	$157.70	3.122%	$162.6234	$162.62	$162.60	$162.60
Purchase #7	$72.50	5.442%	$76.4455	$76.45	$76.45	$76.40
7 purchase totals =	$922.13		$964.0184	$964.02	$964.00	$963.80