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	$186.88	6.202%	$198.4703	$198.47	$198.45	$198.50
Purchase #2	$81.81	10.572%	$90.459	$90.46	$90.45	$90.50
Purchase #3	$151.64	9.691%	$166.3354	$166.34	$166.35	$166.30
Purchase #4	$222.82	13.578%	$253.0745	$253.07	$253.05	$253.10
Purchase #5	$144.75	7.287%	$155.2979	$155.30	$155.30	$155.30
Purchase #6	$139.80	6.216%	$148.49	$148.49	$148.50	$148.50
Purchase #7	$116.25	13.289%	$131.6985	$131.70	$131.70	$131.70
7 purchase totals =	$1,043.95		$1,143.8256	$1,143.83	$1,143.80	$1,143.90