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	$158.59	3.667%	$164.4055	$164.41	$164.40	$164.40
Purchase #2	$213.56	13.105%	$241.547	$241.55	$241.55	$241.50
Purchase #3	$246.61	10.746%	$273.1107	$273.11	$273.10	$273.10
Purchase #4	$156.55	7.265%	$167.9234	$167.92	$167.90	$167.90
Purchase #5	$137.78	13.322%	$156.1351	$156.14	$156.15	$156.10
Purchase #6	$176.54	7.786%	$190.2854	$190.29	$190.30	$190.30
Purchase #7	$57.28	4.259%	$59.7196	$59.72	$59.70	$59.70
7 purchase totals =	$1,146.91		$1,253.1267	$1,253.14	$1,253.10	$1,253.00