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	$165.73	7.119%	$177.5283	$177.53	$177.55	$177.50
Purchase #2	$144.58	13.546%	$164.1648	$164.16	$164.15	$164.20
Purchase #3	$139.37	6.729%	$148.7482	$148.75	$148.75	$148.70
Purchase #4	$23.54	3.647%	$24.3985	$24.40	$24.40	$24.40
Purchase #5	$93.60	10.592%	$103.5141	$103.51	$103.50	$103.50
Purchase #6	$187.39	13.738%	$213.1336	$213.13	$213.15	$213.10
Purchase #7	$111.82	10.806%	$123.9033	$123.90	$123.90	$123.90
7 purchase totals =	$866.03		$955.3908	$955.38	$955.40	$955.30