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	$239.69	12.444%	$269.517	$269.52	$269.50	$269.50
Purchase #2	$214.36	3.712%	$222.317	$222.32	$222.30	$222.30
Purchase #3	$185.71	7.782%	$200.162	$200.16	$200.15	$200.20
Purchase #4	$149.32	12.836%	$168.4867	$168.49	$168.50	$168.50
Purchase #5	$10.74	5.419%	$11.322	$11.32	$11.30	$11.30
Purchase #6	$80.32	4.309%	$83.781	$83.78	$83.80	$83.80
Purchase #7	$86.79	3.735%	$90.0316	$90.03	$90.05	$90.00
7 purchase totals =	$966.93		$1,045.6173	$1,045.62	$1,045.60	$1,045.60