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	$112.44	13.636%	$127.7723	$127.77	$127.75	$127.80
Purchase #2	$58.90	4.686%	$61.6601	$61.66	$61.65	$61.70
Purchase #3	$83.45	9.591%	$91.4537	$91.45	$91.45	$91.50
Purchase #4	$105.71	13.349%	$119.8212	$119.82	$119.80	$119.80
Purchase #5	$180.51	8.207%	$195.3245	$195.32	$195.30	$195.30
Purchase #6	$237.80	10.498%	$262.7642	$262.76	$262.75	$262.80
Purchase #7	$242.85	5.240%	$255.5753	$255.58	$255.60	$255.60
7 purchase totals =	$1,021.66		$1,114.3713	$1,114.36	$1,114.30	$1,114.50