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	$125.25	4.141%	$130.4366	$130.44	$130.45	$130.40
Purchase #2	$148.78	8.132%	$160.8788	$160.88	$160.90	$160.90
Purchase #3	$18.77	13.594%	$21.3216	$21.32	$21.30	$21.30
Purchase #4	$21.88	10.384%	$24.152	$24.15	$24.15	$24.20
Purchase #5	$82.63	13.558%	$93.833	$93.83	$93.85	$93.80
Purchase #6	$43.78	6.425%	$46.5929	$46.59	$46.60	$46.60
Purchase #7	$52.36	7.235%	$56.1482	$56.15	$56.15	$56.10
7 purchase totals =	$493.45		$533.3631	$533.36	$533.40	$533.30