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	$145.74	3.360%	$150.6369	$150.64	$150.65	$150.60
Purchase #2	$130.98	11.244%	$145.7074	$145.71	$145.70	$145.70
Purchase #3	$72.42	8.404%	$78.5062	$78.51	$78.50	$78.50
Purchase #4	$160.60	7.796%	$173.1204	$173.12	$173.10	$173.10
Purchase #5	$238.71	9.126%	$260.4947	$260.49	$260.50	$260.50
Purchase #6	$137.50	4.686%	$143.9433	$143.94	$143.95	$143.90
Purchase #7	$181.95	11.328%	$202.5613	$202.56	$202.55	$202.60
7 purchase totals =	$1,067.90		$1,154.9702	$1,154.97	$1,154.95	$1,154.90