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	$231.92	8.834%	$252.4078	$252.41	$252.40	$252.40
Purchase #2	$98.63	11.165%	$109.642	$109.64	$109.65	$109.60
Purchase #3	$29.82	12.359%	$33.5055	$33.51	$33.50	$33.50
Purchase #4	$57.82	7.406%	$62.1021	$62.10	$62.10	$62.10
Purchase #5	$71.84	9.390%	$78.5858	$78.59	$78.60	$78.60
Purchase #6	$210.83	7.489%	$226.6191	$226.62	$226.60	$226.60
Purchase #7	$10.75	6.352%	$11.4328	$11.43	$11.45	$11.40
7 purchase totals =	$711.61		$774.2951	$774.30	$774.30	$774.20