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	$57.67	3.683%	$59.794	$59.79	$59.80	$59.80
Purchase #2	$132.41	11.715%	$147.9218	$147.92	$147.90	$147.90
Purchase #3	$185.88	12.381%	$208.8938	$208.89	$208.90	$208.90
Purchase #4	$43.44	10.666%	$48.0733	$48.07	$48.05	$48.10
Purchase #5	$230.28	3.600%	$238.5701	$238.57	$238.55	$238.60
Purchase #6	$73.40	12.210%	$82.3621	$82.36	$82.35	$82.40
Purchase #7	$217.68	3.795%	$225.941	$225.94	$225.95	$225.90
7 purchase totals =	$940.76		$1,011.5561	$1,011.54	$1,011.50	$1,011.60