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	$49.86	13.541%	$56.6115	$56.61	$56.60	$56.60
Purchase #2	$143.96	12.589%	$162.0831	$162.08	$162.10	$162.10
Purchase #3	$24.57	11.676%	$27.4388	$27.44	$27.45	$27.40
Purchase #4	$178.55	6.456%	$190.0772	$190.08	$190.10	$190.10
Purchase #5	$204.59	9.462%	$223.9483	$223.95	$223.95	$223.90
Purchase #6	$168.64	7.263%	$180.8883	$180.89	$180.90	$180.90
Purchase #7	$151.91	10.749%	$168.2388	$168.24	$168.25	$168.20
7 purchase totals =	$922.08		$1,009.2860	$1,009.29	$1,009.35	$1,009.20