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	$41.77	13.798%	$47.5334	$47.53	$47.55	$47.50
Purchase #2	$80.86	12.371%	$90.8632	$90.86	$90.85	$90.90
Purchase #3	$172.83	8.702%	$187.8697	$187.87	$187.85	$187.90
Purchase #4	$33.74	10.746%	$37.3657	$37.37	$37.35	$37.40
Purchase #5	$18.43	13.374%	$20.8948	$20.89	$20.90	$20.90
Purchase #6	$17.85	3.871%	$18.541	$18.54	$18.55	$18.50
Purchase #7	$48.39	5.418%	$51.0118	$51.01	$51.00	$51.00
7 purchase totals =	$413.87		$454.0796	$454.07	$454.05	$454.10