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	$204.81	7.866%	$220.9204	$220.92	$220.90	$220.90
Purchase #2	$52.70	12.698%	$59.3918	$59.39	$59.40	$59.40
Purchase #3	$174.31	10.473%	$192.5655	$192.57	$192.55	$192.60
Purchase #4	$230.51	4.167%	$240.1154	$240.12	$240.10	$240.10
Purchase #5	$58.41	11.339%	$65.0331	$65.03	$65.05	$65.00
Purchase #6	$103.75	7.856%	$111.9006	$111.90	$111.90	$111.90
Purchase #7	$119.42	11.494%	$133.1461	$133.15	$133.15	$133.10
7 purchase totals =	$943.91		$1,023.0729	$1,023.08	$1,023.05	$1,023.00