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	$39.96	5.433%	$42.131	$42.13	$42.15	$42.10
Purchase #2	$158.58	11.800%	$177.2924	$177.29	$177.30	$177.30
Purchase #3	$42.83	10.192%	$47.1952	$47.20	$47.20	$47.20
Purchase #4	$184.97	6.414%	$196.834	$196.83	$196.85	$196.80
Purchase #5	$166.42	9.129%	$181.6125	$181.61	$181.60	$181.60
Purchase #6	$172.51	11.328%	$192.0519	$192.05	$192.05	$192.10
Purchase #7	$205.70	5.421%	$216.851	$216.85	$216.85	$216.90
7 purchase totals =	$970.97		$1,053.9680	$1,053.96	$1,054.00	$1,054.00