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	$246.90	5.146%	$259.6055	$259.61	$259.60	$259.60
Purchase #2	$248.51	4.584%	$259.9017	$259.90	$259.90	$259.90
Purchase #3	$18.36	6.184%	$19.4954	$19.50	$19.50	$19.50
Purchase #4	$176.57	13.644%	$200.6612	$200.66	$200.65	$200.70
Purchase #5	$101.43	4.828%	$106.327	$106.33	$106.35	$106.30
Purchase #6	$19.37	8.221%	$20.9624	$20.96	$20.95	$21.00
Purchase #7	$47.47	6.476%	$50.5442	$50.54	$50.55	$50.50
7 purchase totals =	$858.61		$917.4974	$917.50	$917.50	$917.50