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	$64.40	12.621%	$72.5279	$72.53	$72.55	$72.50
Purchase #2	$206.78	3.541%	$214.1021	$214.10	$214.10	$214.10
Purchase #3	$208.71	5.604%	$220.4061	$220.41	$220.40	$220.40
Purchase #4	$107.96	4.746%	$113.0838	$113.08	$113.10	$113.10
Purchase #5	$215.52	10.570%	$238.3005	$238.30	$238.30	$238.30
Purchase #6	$158.45	8.288%	$171.5823	$171.58	$171.60	$171.60
Purchase #7	$138.54	10.797%	$153.4982	$153.50	$153.50	$153.50
7 purchase totals =	$1,100.36		$1,183.5009	$1,183.50	$1,183.55	$1,183.50