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	$56.30	9.149%	$61.4509	$61.45	$61.45	$61.50
Purchase #2	$90.46	9.274%	$98.8493	$98.85	$98.85	$98.80
Purchase #3	$192.43	6.866%	$205.6422	$205.64	$205.65	$205.60
Purchase #4	$156.33	7.724%	$168.4049	$168.40	$168.40	$168.40
Purchase #5	$167.73	10.795%	$185.8365	$185.84	$185.85	$185.80
Purchase #6	$87.70	11.249%	$97.5654	$97.57	$97.55	$97.60
Purchase #7	$249.46	13.327%	$282.7055	$282.71	$282.70	$282.70
7 purchase totals =	$1,000.41		$1,100.4547	$1,100.46	$1,100.45	$1,100.40