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	$97.94	9.128%	$106.88	$106.88	$106.90	$106.90
Purchase #2	$40.81	5.571%	$43.0835	$43.08	$43.10	$43.10
Purchase #3	$75.36	9.362%	$82.4152	$82.42	$82.40	$82.40
Purchase #4	$66.89	4.483%	$69.8887	$69.89	$69.90	$69.90
Purchase #5	$71.74	3.807%	$74.4711	$74.47	$74.45	$74.50
Purchase #6	$12.31	10.353%	$13.5845	$13.58	$13.60	$13.60
Purchase #7	$104.38	12.328%	$117.248	$117.25	$117.25	$117.20
7 purchase totals =	$469.43		$507.5710	$507.57	$507.60	$507.60