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	$203.39	10.874%	$225.5066	$225.51	$225.50	$225.50
Purchase #2	$223.30	8.338%	$241.9188	$241.92	$241.90	$241.90
Purchase #3	$22.62	11.629%	$25.2505	$25.25	$25.25	$25.30
Purchase #4	$96.31	8.526%	$104.5214	$104.52	$104.50	$104.50
Purchase #5	$156.54	4.732%	$163.9475	$163.95	$163.95	$163.90
Purchase #6	$152.82	3.312%	$157.8814	$157.88	$157.90	$157.90
Purchase #7	$143.26	6.464%	$152.5203	$152.52	$152.50	$152.50
7 purchase totals =	$998.24		$1,071.5465	$1,071.55	$1,071.50	$1,071.50