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	$42.89	8.715%	$46.6279	$46.63	$46.65	$46.60
Purchase #2	$164.29	4.422%	$171.5549	$171.55	$171.55	$171.60
Purchase #3	$216.36	7.696%	$233.0111	$233.01	$233.00	$233.00
Purchase #4	$150.74	9.174%	$164.5689	$164.57	$164.55	$164.60
Purchase #5	$159.78	4.459%	$166.9046	$166.90	$166.90	$166.90
Purchase #6	$65.81	4.115%	$68.5181	$68.52	$68.50	$68.50
Purchase #7	$237.39	10.137%	$261.4542	$261.45	$261.45	$261.50
7 purchase totals =	$1,037.26		$1,112.6397	$1,112.63	$1,112.60	$1,112.70