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	$154.64	12.545%	$174.0396	$174.04	$174.05	$174.00
Purchase #2	$35.28	8.139%	$38.1514	$38.15	$38.15	$38.20
Purchase #3	$215.28	10.383%	$237.6325	$237.63	$237.65	$237.60
Purchase #4	$183.27	7.384%	$196.8027	$196.80	$196.80	$196.80
Purchase #5	$151.86	5.493%	$160.2017	$160.20	$160.20	$160.20
Purchase #6	$123.68	3.331%	$127.7998	$127.80	$127.80	$127.80
Purchase #7	$126.94	3.637%	$131.5568	$131.56	$131.55	$131.60
7 purchase totals =	$990.95		$1,066.1845	$1,066.18	$1,066.20	$1,066.20