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	$131.91	10.240%	$145.4176	$145.42	$145.40	$145.40
Purchase #2	$207.69	10.500%	$229.4975	$229.50	$229.50	$229.50
Purchase #3	$207.29	7.152%	$222.1154	$222.12	$222.10	$222.10
Purchase #4	$171.25	3.316%	$176.9287	$176.93	$176.95	$176.90
Purchase #5	$130.99	9.113%	$142.9271	$142.93	$142.95	$142.90
Purchase #6	$26.47	4.298%	$27.6077	$27.61	$27.60	$27.60
Purchase #7	$100.98	8.872%	$109.9389	$109.94	$109.95	$109.90
7 purchase totals =	$976.58		$1,054.4329	$1,054.45	$1,054.45	$1,054.30