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	$6.30	12.219%	$7.0698	$7.07	$7.05	$7.10
Purchase #2	$119.39	10.490%	$131.914	$131.91	$131.90	$131.90
Purchase #3	$154.42	7.540%	$166.0633	$166.06	$166.05	$166.10
Purchase #4	$163.84	7.664%	$176.3967	$176.40	$176.40	$176.40
Purchase #5	$107.55	10.828%	$119.1955	$119.20	$119.20	$119.20
Purchase #6	$136.67	10.737%	$151.3443	$151.34	$151.35	$151.30
Purchase #7	$226.30	10.547%	$250.1679	$250.17	$250.15	$250.20
7 purchase totals =	$914.47		$1,002.1515	$1,002.15	$1,002.10	$1,002.20