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	$189.84	9.693%	$208.2412	$208.24	$208.25	$208.20
Purchase #2	$140.30	3.783%	$145.6075	$145.61	$145.60	$145.60
Purchase #3	$116.53	12.691%	$131.3188	$131.32	$131.30	$131.30
Purchase #4	$186.89	9.273%	$204.2203	$204.22	$204.20	$204.20
Purchase #5	$95.29	8.236%	$103.1381	$103.14	$103.15	$103.10
Purchase #6	$69.30	13.408%	$78.5917	$78.59	$78.60	$78.60
Purchase #7	$99.79	11.830%	$111.5952	$111.60	$111.60	$111.60
7 purchase totals =	$897.94		$982.7128	$982.72	$982.70	$982.60