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	$153.39	8.407%	$166.2855	$166.29	$166.30	$166.30
Purchase #2	$205.60	13.526%	$233.4095	$233.41	$233.40	$233.40
Purchase #3	$56.76	10.505%	$62.7226	$62.72	$62.70	$62.70
Purchase #4	$138.81	12.287%	$155.8656	$155.87	$155.85	$155.90
Purchase #5	$231.46	4.318%	$241.4544	$241.45	$241.45	$241.50
Purchase #6	$36.71	11.264%	$40.845	$40.85	$40.85	$40.80
Purchase #7	$195.78	5.449%	$206.4481	$206.45	$206.45	$206.40
7 purchase totals =	$1,018.51		$1,107.0307	$1,107.04	$1,107.00	$1,107.00