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	$111.59	4.448%	$116.5535	$116.55	$116.55	$116.60
Purchase #2	$132.82	10.371%	$146.5948	$146.59	$146.60	$146.60
Purchase #3	$57.91	8.634%	$62.9099	$62.91	$62.90	$62.90
Purchase #4	$151.67	11.834%	$169.6186	$169.62	$169.60	$169.60
Purchase #5	$203.28	4.395%	$212.2142	$212.21	$212.20	$212.20
Purchase #6	$201.77	7.662%	$217.2296	$217.23	$217.25	$217.20
Purchase #7	$84.71	6.629%	$90.3254	$90.33	$90.35	$90.30
7 purchase totals =	$943.75		$1,015.4460	$1,015.44	$1,015.45	$1,015.40