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	$56.39	5.380%	$59.4238	$59.42	$59.40	$59.40
Purchase #2	$151.76	13.614%	$172.4206	$172.42	$172.40	$172.40
Purchase #3	$220.81	10.787%	$244.6288	$244.63	$244.65	$244.60
Purchase #4	$60.96	13.656%	$69.2847	$69.28	$69.30	$69.30
Purchase #5	$126.56	13.704%	$143.9038	$143.90	$143.90	$143.90
Purchase #6	$55.94	5.381%	$58.9501	$58.95	$58.95	$59.00
Purchase #7	$7.65	4.606%	$8.0024	$8.00	$8.00	$8.00
7 purchase totals =	$680.07		$756.6142	$756.60	$756.60	$756.60