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	$189.50	10.262%	$208.9465	$208.95	$208.95	$208.90
Purchase #2	$147.69	11.503%	$164.6788	$164.68	$164.70	$164.70
Purchase #3	$163.65	8.325%	$177.2739	$177.27	$177.25	$177.30
Purchase #4	$61.52	7.578%	$66.182	$66.18	$66.20	$66.20
Purchase #5	$179.73	6.205%	$190.8822	$190.88	$190.90	$190.90
Purchase #6	$85.67	12.767%	$96.6075	$96.61	$96.60	$96.60
Purchase #7	$175.85	5.149%	$184.9045	$184.90	$184.90	$184.90
7 purchase totals =	$1,003.61		$1,089.4754	$1,089.47	$1,089.50	$1,089.50