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	$40.82	7.644%	$43.9403	$43.94	$43.95	$43.90
Purchase #2	$154.34	8.143%	$166.9079	$166.91	$166.90	$166.90
Purchase #3	$103.59	11.272%	$115.2667	$115.27	$115.25	$115.30
Purchase #4	$121.32	12.572%	$136.5724	$136.57	$136.55	$136.60
Purchase #5	$151.25	4.572%	$158.1652	$158.17	$158.15	$158.20
Purchase #6	$65.29	9.651%	$71.5911	$71.59	$71.60	$71.60
Purchase #7	$65.46	5.593%	$69.1212	$69.12	$69.10	$69.10
7 purchase totals =	$702.07		$761.5648	$761.57	$761.50	$761.60