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	$241.83	8.460%	$262.2888	$262.29	$262.30	$262.30
Purchase #2	$24.35	6.763%	$25.9968	$26.00	$26.00	$26.00
Purchase #3	$51.70	5.133%	$54.3538	$54.35	$54.35	$54.40
Purchase #4	$104.73	6.570%	$111.6108	$111.61	$111.60	$111.60
Purchase #5	$70.67	10.709%	$78.2381	$78.24	$78.25	$78.20
Purchase #6	$245.87	3.507%	$254.4927	$254.49	$254.50	$254.50
Purchase #7	$112.38	4.792%	$117.7652	$117.77	$117.75	$117.80
7 purchase totals =	$851.53		$904.7462	$904.75	$904.75	$904.80