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	$241.72	10.208%	$266.3948	$266.39	$266.40	$266.40
Purchase #2	$93.40	5.610%	$98.6397	$98.64	$98.65	$98.60
Purchase #3	$57.44	8.832%	$62.5131	$62.51	$62.50	$62.50
Purchase #4	$47.85	6.345%	$50.8861	$50.89	$50.90	$50.90
Purchase #5	$70.33	11.804%	$78.6318	$78.63	$78.65	$78.60
Purchase #6	$48.65	3.676%	$50.4384	$50.44	$50.45	$50.40
Purchase #7	$103.74	10.521%	$114.6545	$114.65	$114.65	$114.70
7 purchase totals =	$663.13		$722.1584	$722.15	$722.20	$722.10