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	$224.53	8.622%	$243.889	$243.89	$243.90	$243.90
Purchase #2	$216.41	11.327%	$240.9228	$240.92	$240.90	$240.90
Purchase #3	$233.71	11.643%	$260.9209	$260.92	$260.90	$260.90
Purchase #4	$79.72	4.697%	$83.4644	$83.46	$83.45	$83.50
Purchase #5	$183.29	9.453%	$200.6164	$200.62	$200.60	$200.60
Purchase #6	$223.61	6.641%	$238.4599	$238.46	$238.45	$238.50
Purchase #7	$168.77	9.699%	$185.139	$185.14	$185.15	$185.10
7 purchase totals =	$1,330.04		$1,453.4124	$1,453.41	$1,453.35	$1,453.40