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	$121.34	9.600%	$132.9886	$132.99	$133.00	$133.00
Purchase #2	$127.60	13.589%	$144.9396	$144.94	$144.95	$144.90
Purchase #3	$179.63	5.827%	$190.097	$190.10	$190.10	$190.10
Purchase #4	$64.83	5.603%	$68.4624	$68.46	$68.45	$68.50
Purchase #5	$63.65	12.572%	$71.6521	$71.65	$71.65	$71.70
Purchase #6	$240.82	7.727%	$259.4282	$259.43	$259.45	$259.40
Purchase #7	$141.79	6.852%	$151.5055	$151.51	$151.50	$151.50
7 purchase totals =	$939.66		$1,019.0734	$1,019.08	$1,019.10	$1,019.10