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	$12.89	10.687%	$14.2676	$14.27	$14.25	$14.30
Purchase #2	$104.60	8.259%	$113.2389	$113.24	$113.25	$113.20
Purchase #3	$229.54	11.160%	$255.1567	$255.16	$255.15	$255.20
Purchase #4	$21.71	5.386%	$22.8793	$22.88	$22.90	$22.90
Purchase #5	$20.83	3.341%	$21.5259	$21.53	$21.55	$21.50
Purchase #6	$136.74	5.503%	$144.2648	$144.26	$144.25	$144.30
Purchase #7	$70.27	10.526%	$77.6666	$77.67	$77.65	$77.70
7 purchase totals =	$596.58		$648.9998	$649.01	$649.00	$649.10