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	$41.29	5.333%	$43.492	$43.49	$43.50	$43.50
Purchase #2	$206.61	9.863%	$226.9879	$226.99	$227.00	$227.00
Purchase #3	$170.52	8.850%	$185.611	$185.61	$185.60	$185.60
Purchase #4	$31.31	3.208%	$32.3144	$32.31	$32.30	$32.30
Purchase #5	$7.45	12.873%	$8.409	$8.41	$8.40	$8.40
Purchase #6	$151.65	3.325%	$156.6924	$156.69	$156.70	$156.70
Purchase #7	$64.82	10.175%	$71.4154	$71.42	$71.40	$71.40
7 purchase totals =	$673.65		$724.9221	$724.92	$724.90	$724.90