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	$177.38	12.646%	$199.8115	$199.81	$199.80	$199.80
Purchase #2	$246.30	8.659%	$267.6271	$267.63	$267.65	$267.60
Purchase #3	$233.88	9.206%	$255.411	$255.41	$255.40	$255.40
Purchase #4	$156.96	4.829%	$164.5396	$164.54	$164.55	$164.50
Purchase #5	$162.42	3.184%	$167.5915	$167.59	$167.60	$167.60
Purchase #6	$240.37	8.129%	$259.9097	$259.91	$259.90	$259.90
Purchase #7	$217.30	9.704%	$238.3868	$238.39	$238.40	$238.40
7 purchase totals =	$1,434.61		$1,553.2772	$1,553.28	$1,553.30	$1,553.20