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	$108.72	6.851%	$116.1684	$116.17	$116.15	$116.20
Purchase #2	$38.58	11.521%	$43.0248	$43.02	$43.00	$43.00
Purchase #3	$194.98	12.225%	$218.8163	$218.82	$218.80	$218.80
Purchase #4	$241.82	7.242%	$259.3326	$259.33	$259.35	$259.30
Purchase #5	$108.86	9.787%	$119.5141	$119.51	$119.50	$119.50
Purchase #6	$247.29	3.315%	$255.4877	$255.49	$255.50	$255.50
Purchase #7	$156.39	3.565%	$161.9653	$161.97	$161.95	$162.00
7 purchase totals =	$1,096.64		$1,174.3092	$1,174.31	$1,174.25	$1,174.30