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	$173.76	13.273%	$196.8232	$196.82	$196.80	$196.80
Purchase #2	$207.58	3.362%	$214.5588	$214.56	$214.55	$214.60
Purchase #3	$12.56	4.364%	$13.1081	$13.11	$13.10	$13.10
Purchase #4	$185.56	6.127%	$196.9293	$196.93	$196.95	$196.90
Purchase #5	$58.51	8.545%	$63.5097	$63.51	$63.50	$63.50
Purchase #6	$166.81	6.144%	$177.0588	$177.06	$177.05	$177.10
Purchase #7	$82.64	5.811%	$87.4422	$87.44	$87.45	$87.40
7 purchase totals =	$887.42		$949.4301	$949.43	$949.40	$949.40