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	$234.29	10.521%	$258.9397	$258.94	$258.95	$258.90
Purchase #2	$98.87	4.696%	$103.5129	$103.51	$103.50	$103.50
Purchase #3	$150.85	3.480%	$156.0996	$156.10	$156.10	$156.10
Purchase #4	$240.81	13.201%	$272.5993	$272.60	$272.60	$272.60
Purchase #5	$100.94	10.218%	$111.254	$111.25	$111.25	$111.30
Purchase #6	$147.27	11.196%	$163.7583	$163.76	$163.75	$163.80
Purchase #7	$57.87	5.117%	$60.8312	$60.83	$60.85	$60.80
7 purchase totals =	$1,030.90		$1,126.9950	$1,126.99	$1,127.00	$1,127.00