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	$142.38	6.787%	$152.0433	$152.04	$152.05	$152.00
Purchase #2	$44.78	10.383%	$49.4295	$49.43	$49.45	$49.40
Purchase #3	$172.45	9.162%	$188.2499	$188.25	$188.25	$188.20
Purchase #4	$18.53	13.499%	$21.0314	$21.03	$21.05	$21.00
Purchase #5	$191.51	12.300%	$215.0657	$215.07	$215.05	$215.10
Purchase #6	$83.79	12.782%	$94.5	$94.50	$94.50	$94.50
Purchase #7	$38.44	8.258%	$41.6144	$41.61	$41.60	$41.60
7 purchase totals =	$691.88		$761.9342	$761.93	$761.95	$761.80