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	$189.41	3.533%	$196.1019	$196.10	$196.10	$196.10
Purchase #2	$151.81	5.555%	$160.243	$160.24	$160.25	$160.20
Purchase #3	$6.96	6.767%	$7.431	$7.43	$7.45	$7.40
Purchase #4	$60.57	10.861%	$67.1485	$67.15	$67.15	$67.10
Purchase #5	$75.29	4.526%	$78.6976	$78.70	$78.70	$78.70
Purchase #6	$51.60	12.117%	$57.8524	$57.85	$57.85	$57.90
Purchase #7	$194.52	5.645%	$205.5007	$205.50	$205.50	$205.50
7 purchase totals =	$730.16		$772.9751	$772.97	$773.00	$772.90