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	$226.72	6.303%	$241.0102	$241.01	$241.00	$241.00
Purchase #2	$247.86	13.163%	$280.4858	$280.49	$280.50	$280.50
Purchase #3	$245.93	9.467%	$269.2122	$269.21	$269.20	$269.20
Purchase #4	$187.98	6.664%	$200.507	$200.51	$200.50	$200.50
Purchase #5	$100.67	8.438%	$109.1645	$109.16	$109.15	$109.20
Purchase #6	$244.85	3.278%	$252.8762	$252.88	$252.90	$252.90
Purchase #7	$240.45	9.571%	$263.4635	$263.46	$263.45	$263.50
7 purchase totals =	$1,494.46		$1,616.7194	$1,616.72	$1,616.70	$1,616.80