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	$101.80	3.389%	$105.25	$105.25	$105.25	$105.30
Purchase #2	$11.97	13.851%	$13.628	$13.63	$13.65	$13.60
Purchase #3	$182.40	9.548%	$199.8156	$199.82	$199.80	$199.80
Purchase #4	$87.43	6.420%	$93.043	$93.04	$93.05	$93.00
Purchase #5	$38.78	11.227%	$43.1338	$43.13	$43.15	$43.10
Purchase #6	$56.33	5.347%	$59.342	$59.34	$59.35	$59.30
Purchase #7	$127.56	7.240%	$136.7953	$136.80	$136.80	$136.80
7 purchase totals =	$606.27		$651.0077	$651.01	$651.05	$650.90