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	$156.45	12.532%	$176.0563	$176.06	$176.05	$176.10
Purchase #2	$80.96	10.725%	$89.643	$89.64	$89.65	$89.60
Purchase #3	$19.60	10.554%	$21.6686	$21.67	$21.65	$21.70
Purchase #4	$40.47	6.592%	$43.1378	$43.14	$43.15	$43.10
Purchase #5	$19.93	8.785%	$21.6809	$21.68	$21.70	$21.70
Purchase #6	$142.47	3.593%	$147.5889	$147.59	$147.60	$147.60
Purchase #7	$207.44	8.213%	$224.477	$224.48	$224.50	$224.50
7 purchase totals =	$667.32		$724.2525	$724.26	$724.30	$724.30