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	$12.78	9.578%	$14.0041	$14.00	$14.00	$14.00
Purchase #2	$186.52	12.813%	$210.4188	$210.42	$210.40	$210.40
Purchase #3	$32.29	9.584%	$35.3847	$35.38	$35.40	$35.40
Purchase #4	$92.81	13.230%	$105.0888	$105.09	$105.10	$105.10
Purchase #5	$35.53	8.231%	$38.4545	$38.45	$38.45	$38.50
Purchase #6	$44.75	12.849%	$50.4999	$50.50	$50.50	$50.50
Purchase #7	$17.72	13.526%	$20.1168	$20.12	$20.10	$20.10
7 purchase totals =	$422.40		$473.9676	$473.96	$473.95	$474.00