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	$98.83	7.721%	$106.4607	$106.46	$106.45	$106.50
Purchase #2	$167.60	11.836%	$187.4371	$187.44	$187.45	$187.40
Purchase #3	$40.93	6.182%	$43.4603	$43.46	$43.45	$43.50
Purchase #4	$164.89	12.473%	$185.4567	$185.46	$185.45	$185.50
Purchase #5	$187.29	9.812%	$205.6669	$205.67	$205.65	$205.70
Purchase #6	$59.35	8.169%	$64.1983	$64.20	$64.20	$64.20
Purchase #7	$35.96	12.346%	$40.3996	$40.40	$40.40	$40.40
7 purchase totals =	$754.85		$833.0796	$833.09	$833.05	$833.20