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	$203.86	5.853%	$215.7919	$215.79	$215.80	$215.80
Purchase #2	$237.72	5.758%	$251.4079	$251.41	$251.40	$251.40
Purchase #3	$247.56	13.314%	$280.5201	$280.52	$280.50	$280.50
Purchase #4	$49.49	12.646%	$55.7485	$55.75	$55.75	$55.70
Purchase #5	$153.88	12.166%	$172.601	$172.60	$172.60	$172.60
Purchase #6	$7.49	11.394%	$8.3434	$8.34	$8.35	$8.30
Purchase #7	$224.32	7.359%	$240.8277	$240.83	$240.85	$240.80
7 purchase totals =	$1,124.32		$1,225.2405	$1,225.24	$1,225.25	$1,225.10