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	$239.44	12.592%	$269.5903	$269.59	$269.60	$269.60
Purchase #2	$200.42	4.677%	$209.7936	$209.79	$209.80	$209.80
Purchase #3	$119.75	3.270%	$123.6658	$123.67	$123.65	$123.70
Purchase #4	$153.66	5.366%	$161.9054	$161.91	$161.90	$161.90
Purchase #5	$28.66	11.643%	$31.9969	$32.00	$32.00	$32.00
Purchase #6	$154.52	11.252%	$171.9066	$171.91	$171.90	$171.90
Purchase #7	$51.49	6.636%	$54.9069	$54.91	$54.90	$54.90
7 purchase totals =	$947.94		$1,023.7655	$1,023.78	$1,023.75	$1,023.80