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	$147.70	9.839%	$162.2322	$162.23	$162.25	$162.20
Purchase #2	$174.72	8.323%	$189.2619	$189.26	$189.25	$189.30
Purchase #3	$99.75	11.778%	$111.4986	$111.50	$111.50	$111.50
Purchase #4	$35.32	8.174%	$38.2071	$38.21	$38.20	$38.20
Purchase #5	$32.80	12.501%	$36.9003	$36.90	$36.90	$36.90
Purchase #6	$188.47	10.719%	$208.6721	$208.67	$208.65	$208.70
Purchase #7	$109.82	10.279%	$121.1084	$121.11	$121.10	$121.10
7 purchase totals =	$788.58		$867.8806	$867.88	$867.85	$867.90