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	$23.50	8.849%	$25.5795	$25.58	$25.60	$25.60
Purchase #2	$78.99	13.235%	$89.4443	$89.44	$89.45	$89.40
Purchase #3	$88.45	11.225%	$98.3785	$98.38	$98.40	$98.40
Purchase #4	$147.65	11.522%	$164.6622	$164.66	$164.65	$164.70
Purchase #5	$209.53	5.633%	$221.3328	$221.33	$221.35	$221.30
Purchase #6	$220.37	8.173%	$238.3808	$238.38	$238.40	$238.40
Purchase #7	$205.98	13.812%	$234.43	$234.43	$234.45	$234.40
7 purchase totals =	$974.47		$1,072.2081	$1,072.20	$1,072.30	$1,072.20