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	$78.55	11.530%	$87.6068	$87.61	$87.60	$87.60
Purchase #2	$224.51	13.602%	$255.0479	$255.05	$255.05	$255.00
Purchase #3	$179.31	11.681%	$200.2552	$200.26	$200.25	$200.30
Purchase #4	$135.55	9.473%	$148.3907	$148.39	$148.40	$148.40
Purchase #5	$235.70	8.608%	$255.9891	$255.99	$256.00	$256.00
Purchase #6	$38.44	9.493%	$42.0891	$42.09	$42.10	$42.10
Purchase #7	$23.35	9.272%	$25.515	$25.52	$25.50	$25.50
7 purchase totals =	$915.41		$1,014.8938	$1,014.91	$1,014.90	$1,014.90