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	$209.96	7.339%	$225.369	$225.37	$225.35	$225.40
Purchase #2	$200.49	3.777%	$208.0625	$208.06	$208.05	$208.10
Purchase #3	$217.44	6.353%	$231.254	$231.25	$231.25	$231.30
Purchase #4	$40.57	7.691%	$43.6902	$43.69	$43.70	$43.70
Purchase #5	$87.41	10.778%	$96.831	$96.83	$96.85	$96.80
Purchase #6	$225.77	8.283%	$244.4705	$244.47	$244.45	$244.50
Purchase #7	$34.68	9.408%	$37.9427	$37.94	$37.95	$37.90
7 purchase totals =	$1,016.32		$1,087.6199	$1,087.61	$1,087.60	$1,087.70