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	$14.95	8.596%	$16.2351	$16.24	$16.25	$16.20
Purchase #2	$166.90	3.506%	$172.7515	$172.75	$172.75	$172.80
Purchase #3	$82.39	7.316%	$88.4177	$88.42	$88.40	$88.40
Purchase #4	$38.59	5.188%	$40.592	$40.59	$40.60	$40.60
Purchase #5	$145.31	13.631%	$165.1172	$165.12	$165.10	$165.10
Purchase #6	$201.80	9.785%	$221.5461	$221.55	$221.55	$221.50
Purchase #7	$108.39	7.560%	$116.5843	$116.58	$116.60	$116.60
7 purchase totals =	$758.33		$821.2439	$821.25	$821.25	$821.20