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	$51.41	9.407%	$56.2461	$56.25	$56.25	$56.20
Purchase #2	$145.69	8.793%	$158.5005	$158.50	$158.50	$158.50
Purchase #3	$222.76	7.218%	$238.8388	$238.84	$238.85	$238.80
Purchase #4	$234.53	8.156%	$253.6583	$253.66	$253.65	$253.70
Purchase #5	$119.47	7.478%	$128.404	$128.40	$128.40	$128.40
Purchase #6	$63.36	10.673%	$70.1224	$70.12	$70.10	$70.10
Purchase #7	$246.34	13.734%	$280.1723	$280.17	$280.15	$280.20
7 purchase totals =	$1,083.56		$1,185.9424	$1,185.94	$1,185.90	$1,185.90