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	$140.99	3.165%	$145.4523	$145.45	$145.45	$145.50
Purchase #2	$35.57	13.298%	$40.3001	$40.30	$40.30	$40.30
Purchase #3	$40.33	11.329%	$44.899	$44.90	$44.90	$44.90
Purchase #4	$245.82	10.813%	$272.4005	$272.40	$272.40	$272.40
Purchase #5	$33.52	6.354%	$35.6499	$35.65	$35.65	$35.60
Purchase #6	$222.25	7.439%	$238.7832	$238.78	$238.80	$238.80
Purchase #7	$148.62	9.451%	$162.6661	$162.67	$162.65	$162.70
7 purchase totals =	$867.10		$940.1511	$940.15	$940.15	$940.20