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	$234.55	12.331%	$263.4724	$263.47	$263.45	$263.50
Purchase #2	$152.73	13.629%	$173.5456	$173.55	$173.55	$173.50
Purchase #3	$49.47	6.215%	$52.5446	$52.54	$52.55	$52.50
Purchase #4	$15.26	5.240%	$16.0596	$16.06	$16.05	$16.10
Purchase #5	$221.46	4.575%	$231.5918	$231.59	$231.60	$231.60
Purchase #6	$179.67	6.223%	$190.8509	$190.85	$190.85	$190.90
Purchase #7	$12.61	5.469%	$13.2996	$13.30	$13.30	$13.30
7 purchase totals =	$865.75		$941.3645	$941.36	$941.35	$941.40