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	$231.55	13.820%	$263.5502	$263.55	$263.55	$263.60
Purchase #2	$154.45	11.821%	$172.7075	$172.71	$172.70	$172.70
Purchase #3	$12.53	10.470%	$13.8419	$13.84	$13.85	$13.80
Purchase #4	$178.50	8.125%	$193.0031	$193.00	$193.00	$193.00
Purchase #5	$40.31	7.745%	$43.432	$43.43	$43.45	$43.40
Purchase #6	$152.45	8.138%	$164.8564	$164.86	$164.85	$164.90
Purchase #7	$194.73	7.240%	$208.8285	$208.83	$208.85	$208.80
7 purchase totals =	$964.52		$1,060.2196	$1,060.22	$1,060.25	$1,060.20