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	$159.58	10.575%	$176.4556	$176.46	$176.45	$176.50
Purchase #2	$111.80	10.514%	$123.5547	$123.55	$123.55	$123.60
Purchase #3	$145.36	3.691%	$150.7252	$150.73	$150.75	$150.70
Purchase #4	$59.94	8.459%	$65.0103	$65.01	$65.00	$65.00
Purchase #5	$160.30	7.368%	$172.1109	$172.11	$172.10	$172.10
Purchase #6	$151.36	6.196%	$160.7383	$160.74	$160.75	$160.70
Purchase #7	$198.90	13.427%	$225.6063	$225.61	$225.60	$225.60
7 purchase totals =	$987.24		$1,074.2013	$1,074.21	$1,074.20	$1,074.20