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	$210.37	12.870%	$237.4446	$237.44	$237.45	$237.40
Purchase #2	$132.38	12.489%	$148.9129	$148.91	$148.90	$148.90
Purchase #3	$82.81	7.354%	$88.8998	$88.90	$88.90	$88.90
Purchase #4	$157.93	3.323%	$163.178	$163.18	$163.20	$163.20
Purchase #5	$126.93	11.570%	$141.6158	$141.62	$141.60	$141.60
Purchase #6	$80.37	11.805%	$89.8577	$89.86	$89.85	$89.90
Purchase #7	$207.61	11.113%	$230.6817	$230.68	$230.70	$230.70
7 purchase totals =	$998.40		$1,100.5905	$1,100.59	$1,100.60	$1,100.60