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	$133.28	7.164%	$142.8282	$142.83	$142.85	$142.80
Purchase #2	$235.72	8.403%	$255.5276	$255.53	$255.55	$255.50
Purchase #3	$180.37	8.788%	$196.2209	$196.22	$196.20	$196.20
Purchase #4	$44.93	3.120%	$46.3318	$46.33	$46.35	$46.30
Purchase #5	$50.64	9.596%	$55.4994	$55.50	$55.50	$55.50
Purchase #6	$181.68	4.223%	$189.3523	$189.35	$189.35	$189.40
Purchase #7	$103.34	10.443%	$114.1318	$114.13	$114.15	$114.10
7 purchase totals =	$929.96		$999.8920	$999.89	$999.95	$999.80